The pick and roll explained: every answer leaves a man

Two attackers, two defenders, twenty feet from the basket. That is the whole thing. The pick and roll in basketball is usually explained as a play, which is the one description it does not deserve, because a play is a sequence you run and this is a question you ask. One man stands still in the path of another man's defender. From that instant the defence has to decide which of two attackers it is prepared to leave open, and there is no option on the menu that leaves nobody.

That is the argument of everything below. Not that the action is clever, or that it is hard to execute, because it is neither. It is that the action is unanswerable in principle, and the four coverages a defence can run against it are not solutions. They are four different ways of paying.

The question the pick and roll asks, and why there is no correct answer

Start with the on-ball defender, because he is the man the screen is aimed at.

His job is to stay between the ball and the basket, and he does it by mirroring, staying on the ball handler's hip, moving where the ball moves. A screen removes his shortest route. Suddenly the path he needs is occupied by a body he is not allowed to run through, and he has three options: go over the top of the screen, go under it, or squeeze through the gap between the screener and his own teammate. Each of those takes time. Not much time. Perhaps half a second, sometimes less.

Half a second is the entire product being manufactured here.

Now look at the only defender who is close enough to cover that half second, which is the screener's defender. He can step out and delay the ball handler, and if he does, he has left the screener. He can stay with the screener, and if he does, he has left the ball handler with a free run at whatever is behind him. He is being asked to be in two places, and the two places move apart from each other at the speed of two athletes running in opposite directions.

That is the question. One defender, two threats, at the same moment. Everything else in the sport's defensive vocabulary is either a way of paying that bill or a way of borrowing from somebody else to pay it.

What makes it the most-run action in professional basketball is not the difficulty of the question, though. It is the repeatability. A set play is a piece of choreography that works once, maybe twice, before a defence that has watched film knows the third cut before it happens. A ball screen is not choreography. It can be set anywhere on the floor, at any angle, at any second on the shot clock, by any two players, and it can be run again immediately if the first one produced nothing. It scales, it repeats, and it does not require the defence to be surprised. A defence can know exactly what is coming, say it out loud, prepare for it all week, and still have to answer the question.

• 4Players the action directly involves
• 2Defenders committed to the ball on a blitz
• 4Attackers the remaining three defenders must cover
• 3Seconds a defender may stay in the paint unattached

Structural counts, not statistics. Two attackers and their two defenders are directly involved; a blitz sends two defenders to the ball; the defensive three-second rule is the published clause that stops a defence simply parking a rim protector under the basket.

The last line of that figure matters more than it looks. Without the defensive three-second rule, the answer to every ball screen would be to leave a seven-footer standing under the basket permanently, and the action would be far less dangerous than it is. The rule forces the rim protector to be attached to somebody, which means the offence can drag him away from the rim by choosing who he guards. The rulebook is a participant in this argument, not a neutral backdrop to it.

What actually makes a screen legal, and why it gets whistled

The screen is a piece of legal choreography before it is a tactical one, and most descriptions skip the rules entirely, which is a shame because the rules explain nearly every stylistic detail of how screens are set.

The screener's obligations, as the rulebook frames them, come down to four prohibitions. He may not take up a position closer than a normal step from an opponent who is stationary and cannot see him coming. Against an opponent who is moving, he must leave enough room for that opponent to stop or change direction, and how much room counts as enough scales with how fast the opponent is travelling. He may not make contact by extending a hip, knee, forearm or leg outside the space his own body occupies, the vertical column that the international rules call the cylinder. And having taken a legal position, he may not then move sideways or forwards into the man he is screening.

Read those four together and a single principle falls out. The screener is allowed to occupy space. He is not allowed to deliver force.

That is why a good screen looks so undramatic. The screener arrives early, plants both feet, makes himself wide within his own frame, and then absorbs whatever the defender runs into. A screener who lunges, leans, or swings a hip at the last moment is doing the one thing the rule specifically forbids, and it is also the version that gets called, because movement into a defender is visible from twenty rows up in a way that the exact distance between two players is not. Officials call the fourth prohibition far more often than the first.

Two consequences follow, and both are constantly visible.

The first is that the angle of the screen matters more than the contact. The screener is not trying to hit the defender, he is trying to stand in the longer of the defender's two escape routes. A screen set square to the sideline gives the defender a choice of going over the top or under; a screen set with the screener's back turned towards the baseline, which coaches usually call a step-up screen, uses the sideline itself as a second defender and leaves the man being screened with only one direction to go. The screen's job is to make one of the routes obviously worse, and then let the defender pick it.

The second is that being early is worth more than being physical, which is where the slip comes from. A slip is a screen that never quite happens: the screener sprints into position as though he is going to set one, then peels away towards the basket at the exact moment his defender steps out to prepare for a screen that is not coming. Nothing about it is illegal, because no contact was attempted. It works precisely because the defence has to start reacting to a screen before the screen exists. The same logic produces the ghost screen, where the screener runs across the ball handler's face and out to the arc without ever stopping. Both are actions that exploit the defence's obligation to pre-commit.

And when the first screen produces nothing, the screener simply turns round and sets another one, usually to the opposite side. The re-screen is the cheapest counter in the sport. It costs two seconds and it forces the defence to make the same impossible decision a second time, from a worse starting position, because the on-ball defender is already tired and already behind.

The ball handler is reading one defender, not the whole floor

The common description of the ball handler's job is that he "reads the defence". That is too vague to be useful and it is also not what he does. He reads one man, and the rest is arithmetic he has already done in practice.

The man he reads is the screener's defender, and specifically that defender's feet and hips at the moment of contact. There are only so many places that man can be, and each one has an answer attached to it before the possession starts.

He is retreating towards the basket. He has told the ball handler he will not contest a jump shot. The answer is the shot, taken immediately, off the first dribble past the screen, before the on-ball defender has caught up. Hesitating here is the mistake, because the whole value of the shot is the half second in which nobody is near it.

He is standing level with the screen, upright, in a flat stance. He is trying to do both jobs at once and doing neither. The answer is to snake: the ball handler dribbles hard off the screen, then cuts back across the screener's original position, dragging the big man sideways and putting him on his back rather than in front of him. Snaking is the single most under-explained move in the action. It converts a coverage that was designed to keep the ball on one side into a straight drive at a defender who is now running the wrong way.

He has stepped out above the screen. He is committing to the ball, which means the screener is unguarded for as long as it takes somebody else to arrive. The answer is the pocket pass, a short bounce pass delivered under the hedging defender's arm into the space between him and the retreating help. The window is roughly the length of one step. Wait for certainty and the window closes.

He is angled sideways, chest turned towards the sideline. He is icing the screen, refusing to let the ball into the middle of the floor. The answer is not to force it. It is to reject the screen entirely and drive the other way, or to accept the baseline and make the help defence show itself.

Two more reads belong to the ball handler rather than to the coverage. The first is tempo. A ball handler who comes off a screen at full speed forces a fast decision from the defence, which is sometimes what he wants and sometimes exactly what he does not; a hesitation, a stutter, a slow first step, all of them exist to make the big man commit before the ball handler has committed to anything. Whoever moves second wins that exchange.

The second is a threshold rather than a read. Two feet in the paint changes the possession. Up to that point, help is optional, and a defence can reasonably decide to hold its shape and live with a contested jump shot. Once the ball is properly inside the arc with a defender behind it rather than in front of it, help stops being optional, somebody has to leave somebody, and the offence has moved from asking a question to collecting an answer. Everything in the ball handler's toolkit, the snake, the hesitation, the rejected screen, is aimed at getting to that threshold rather than at scoring directly.

Roll or pop is a question about which defender you want to move

The screener's decision after contact looks like a preference and is actually a target selection. He is choosing which defender he wants to pull out of position, and the two options pull different ones.

The roll is an attack on rim protection. The screener turns his shoulders towards the basket and runs at it, and the important thing about that run is that it is dangerous whether or not the ball ever arrives. A man moving towards the rim with a step on his defender has to be accounted for, and accounting for him is what forces a third defender to leave somebody. The roller who never touches the ball still did his job if a help defender took two steps towards him.

There is craft in it that rarely gets described. The roller does not run in a straight line to the rim, he rolls to the space where his own defender is not, usually sealing that defender behind his back with a forearm as he turns. He keeps his hands up and available, because the pass may come at the pocket, on the short roll, or as a lob. And the lob is not a highlight, it is a punishment: it is the specific answer to a help defender who tags low, because a defender stepping in at waist height cannot then contest a ball thrown above his head.

The pop is an attack on the defence's willingness to leave the paint. When the screener steps back behind the arc instead of rolling, the big man guarding him has to choose between staying near the basket and closing out twenty-four feet from it. A drop coverage is built on the assumption that its big man is allowed to stay home; a screener who can shoot removes the assumption. That is the whole reason the shooting big became a structural piece rather than a curiosity, and it is why a team facing one often has to abandon its preferred coverage entirely.

The pop is worse against a switch, though, and that asymmetry is worth holding on to. After a switch, popping puts a big man on the arc guarded by a smaller, quicker defender, which is the one matchup where the big is least advantaged. Rolling after a switch puts him under the basket with a guard on his back, which is the matchup he wants. The screener's best decision is therefore not fixed, it depends on the coverage he has just seen, which means he is reading his own defender at the same time as the ball handler is.

Between the two sits the short roll, which deserves its own section, because it is the counter to the most aggressive thing a defence can do.

The four coverages, and precisely what each one concedes

Everything a defence does against a ball screen belongs to one of four families. The names vary by organisation, the principles do not, and the reason to learn them as a set is that each is defined by its concession rather than by its technique. A fuller tour of how these fit into a whole-team plan sits in the way NBA defensive schemes are assembled, but the four answers themselves are simple to state.

Switch. The two defenders trade assignments as the screen arrives. The screener's defender picks up the ball handler, the ball handler's defender picks up the screener, and the screen has achieved nothing at all. This is the only coverage that requires no help, no rotation, and no third defender to leave anybody, which is why it is so attractive: the three off-ball defenders never move, so three shooters stay guarded and the defence's shape survives intact. What it concedes is a mismatch, and it concedes it by invitation, because the offence now chooses which pairing it wants and can screen repeatedly until it gets one. It also concedes the offensive glass, since a guard is now boxing out a much larger man. The mechanics of doing this well, including who is allowed to switch onto whom, are worth reading about separately in how a switching defence actually holds up.

Drop. The screener's defender retreats towards the basket while the on-ball defender fights over the top of the screen, aiming to arrive before the shot goes up. The rim is protected, nobody helps, nobody rotates, and the possession is contained without any of the other four defenders being touched. What it concedes is the pull-up jump shot from wherever the screen was set. That was a perfectly reasonable thing to concede when the shot in question was a contested eighteen-footer. Against a ball handler who is comfortable shooting from several feet behind the arc, the concession is enormous, and the depth of the drop becomes a dial rather than a switch: at the level of the screen, at the elbow, at the restricted area, each a different trade between the shot conceded and the layup prevented. Drop coverage and its variations make up the most-used answer in the sport and the most attacked.

Hedge and blitz. Both send the screener's defender out at the ball, and they differ in commitment. A hedge is a temporary show: step out, stall the ball handler for a beat, then retreat to the screener. A blitz is a real double team, two defenders on the ball, hands high, with the explicit aim of forcing a pass out of the best player's hands. Both concede the same thing in different sizes, which is numbers behind the ball. Two defenders on one attacker means three defenders on four attackers everywhere else, and the offence did not have to do anything clever to obtain that.

Ice. Also called down, or blue, depending on whose staff you are listening to. It only works on a screen set at the side of the floor. The on-ball defender jumps to the topside of the screen, refusing to let the ball go towards the middle, and the screener's defender sits back near the baseline. The ball handler is pushed down the sideline into a corner of the court where the sideline and the baseline do half of the defending. What it concedes is the baseline drive into whatever help exists and a shot from the short corner, plus, more importantly, the pop, since the screener is now standing unguarded behind the arc while his man sits in the paint. The offence's simplest counter is to refuse the invitation and re-screen from the other side, which forces the defence to change coverage mid-possession.

There is a fifth answer that is really a degenerate case of the drop, sometimes called weak or under: the on-ball defender goes underneath the screen instead of over it, taking the shortest route back to the ball handler's outside shoulder. It concedes the jump shot completely and unambiguously, and it exists for exactly one situation, which is a ball handler who cannot make that shot. Against anyone who can, it is not a coverage, it is a gift with a ribbon on it.

Blitz, four-on-three converted at 62% on twos1.24pts

Drop, pull-up three made at 38%1.14pts

Switch, mismatch two made at 50%1pts

Ice, short-corner two made at 42%0.84pts

An invented, deliberately round illustration. Each figure is the make rate multiplied by the points the shot pays, for the shot that coverage has chosen to allow. None of these rates is reported from any real team, player or season; they are chosen to show the shape of the trade-off.

Show the numbers

Worked example: what each coverage's concession is worth per possession

Item	Value
Blitz, four-on-three converted at 62% on twos	1.24pts
Drop, pull-up three made at 38%	1.14pts
Switch, mismatch two made at 50%	1pts
Ice, short-corner two made at 42%	0.84pts

Read that figure as a shape rather than as numbers, because the numbers are invented. The shape is the point: the more aggressively a defence attacks the ball, the more it concedes behind the ball, and the more it protects the space behind the ball, the better the shot it hands to the man holding it. There is no column that pays nothing. A coverage is a preference between bills, and a defence that claims to have solved the ball screen has simply stopped noticing which bill it is paying.

The short roll is the price a defence pays for taking the ball away

The blitz is the most tempting coverage in basketball because it does the one thing every coach wants, which is to remove the best player's hands from the decision. It is also the coverage with the sharpest counter, and the counter has a name.

When two defenders commit to the ball, the screener is unguarded and there are three defenders left to cover four attackers. A screener who rolls all the way to the rim runs past the advantage: he ends up under the basket with two help defenders converging, catching in traffic, at the exact moment the defence has finished rotating. A screener who stops halfway, around the free-throw line, catches the ball behind the double team with the whole defence in front of him and a numerical advantage that has not yet decayed.

That is the short roll. The screener stops being a finisher and becomes the passer, and the possession is now decided by whether a large man can make a two-second read while moving.

The reads available to him are not complicated, and that is the point. If the weak-side helper steps up to meet him, the shooter that helper left is open, usually in the corner. If the helper stays attached to his shooter, nobody is between the screener and the rim, and he should simply go there. If two defenders split the difference, both are wrong and the ball goes over the top of them to a cutter. He does not need to see the whole floor. He needs to see one defender's feet, which is exactly the same skill the ball handler exercised half a second earlier.

What makes this the hinge of the modern game is a fact about advantages: they decay with every pass. A four-on-three does not score on its own. The defence is rotating from the moment the pass leaves the ball handler's hands, and each subsequent pass gives the rotation another beat to catch up. A rough working rule, and it is a rule of thumb rather than a measurement, is that an offence has about two passes before the defence has re-established itself. If the shot has not gone up by then, the advantage has been spent and the possession restarts from nothing.

Which produces a blunt strategic conclusion. A blitz is only as costly as the offence's second-best decision-maker. Against a team whose screener can pass on the move, sending two at the ball hands over a four-on-three every single time and is close to unplayable. Against a team whose screener catches the short roll and looks for somebody to give it back to, blitzing is free, and a defence should do it on every possession until it stops being free.

1. 1The screen is set at the top of the keyThe screener plants both feet a step outside the ball handler's defender's route and absorbs the contact without leaning into it. Nothing illegal has happened; a body is simply occupying the shortest path.
2. 2Two defenders go to the ballThe screener's defender jumps out high with his hands up while the on-ball defender fights over the top. The ball handler is now trapped near the sideline with no dribble available towards the middle.
3. 3The screener stops halfwayInstead of rolling to the rim, he pulls up around the free-throw line. He catches a pass thrown over the trap, and there are now three defenders responsible for four attackers, all of them in front of him.
4. 4The weak-side defender has to chooseHe is guarding a shooter in the far corner and he is the only man with a route to the rim. If he stays, the screener walks in for a layup. If he goes, his shooter is alone.
5. 5He tags the rollerTwo steps into the paint, enough to stall the drive. This is the correct decision by the rules of the coverage and it is also the moment the defence stops guarding five men.
6. 6The pass is already goneThe screener read the tag as it began and skipped the ball to the far corner before the helper had finished the step, so the contest that was supposed to happen never gets started.
7. 7The closeout is the longest one on the floorThe nearest remaining defender has to cover the distance from the middle of the paint to the corner, arriving late and arriving at speed, which is the worst possible way to arrive.
8. 8The offence takes whichever half he givesFly at the shooter and he goes past him along the baseline to a rim nobody is guarding. Pull up short and the corner shot goes up with a hand nowhere near it.
9. 9The defence never recovers its shapeThe two trappers are still above the free-throw line. Whatever happens next, the possession is being defended by three men who are each guarding somebody else's assignment.

A step-by-step account of a single constructed possession, describing the sequence of decisions rather than reporting any figures. Every defensive choice in it is individually defensible.

Nothing in that sequence was a mistake. The trap was correct, the tag was correct, the closeout was as fast as a human can run. The defence lost the possession at the moment it decided which of five men it was willing to leave, and everything after that was arithmetic.

The tag and the rotation are where the possession is really decided

The third defender is the least discussed player in the action and the most important one, because he is the only person on the floor who voluntarily stops guarding somebody.

Tagging is the specific act. A defender guarding an off-ball attacker takes a step or two into the rolling screener's path, does not switch onto him, does not stay with him, and gets back out. He is buying time, usually about the length of a stride, for the screener's own defender to recover from wherever the coverage sent him. Done well it is almost invisible. Done late it is a layup, and done too early it is an open shot for the man he left.

Who does the tagging is the actual scheme decision, and it is made before the game rather than during it. There are two main philosophies and they lead to completely different-looking defences.

Tag from the baseline. The low man, usually the defender guarding a corner, steps in. His route to the ball is the shortest, so the tag arrives fastest and the roll is stopped hardest. The cost is that his man is standing in the corner, which is the hardest place on the floor to close out to, since the closeout has a sideline behind it and a baseline beside it and no room to recover if he is beaten. Tagging from the corner buys the best delay at the worst price.

Tag from the top. The defender standing near the free-throw line, guarding a man above the arc, drops in instead. His closeout when he recovers is shorter and he has the whole floor behind him to retreat into. The cost is that his tag arrives later, because he is starting further from the rim, so the roll gets deeper before it is stalled.

After the tag comes the rotation, and this is where defensive schemes actually differ from one another. If the tagger's man receives the ball, somebody else has to take him, which means the defenders behind the ball rotate around each other, usually with the nearest perimeter defender sprinting to the corner while the tagger recovers to the man one pass higher. That exchange, which coaches generally call an x-out, is the most frequently botched sequence in team defence and the one worth watching for if you want to know how well drilled a team is. Whether the rotation is even attempted, or whether the defence prefers to concede the pass rather than move at all, is the substance of how help defence is organised as a system.

The choice of tagger is not made on principle. It is made from a scouting report, and it says something explicit about the opponent. A defence tags from whoever it is least frightened of. If the man in the corner cannot shoot, his defender does the tagging all night and the coverage barely costs anything. If all four off-ball attackers are threats, there is no cheap tagger, the defence has to pick the least bad option, and the offence gets to punish it every time. This is why the same team will run four different coverages against four different opponents in a week without changing a single principle.

40%20%40%

• Trapping the ball2
• Tagging the roller1
• Covering three spaced shooters2

A structural breakdown of one coverage, not a measurement. Two defenders trap the ball, one steps in to stall the roller, and two are left responsible for the three attackers spaced around the arc.

Show the numbers

Where the five defenders are during a blitz

Item	Value
Trapping the ball	2
Tagging the roller	1
Covering three spaced shooters	2

That figure is the entire cost of a blitz in three rows. Two defenders are doing one job, one defender is doing half a job, and two defenders are covering three men. No amount of effort fixes a shortage of bodies.

Why the action scales up when three shooters stand still

Everything above assumed the other three attackers were somewhere. Where they stand determines how expensive every coverage is, and the modern arrangement, two men in the corners and one on the opposite wing, exists to make the tag as costly as possible. The reason a floor full of shooters lengthens every defensive rotation is set out at length in what the three-point line did to defensive geometry, and the short version is that the help has to start further away and travel further to arrive.

What matters here is the specific effect on the two-man action, and it is sharper than the general argument about spacing suggests.

Consider the empty corner version, where the offence deliberately removes the attacker from the corner on the side the screen is set. Most people watching assume this is a mistake, because the corner is a good place to stand. The point is the opposite: with nobody in that corner, there is no defender in that corner either, which means the nearest available tagger is on the far side of the floor and has an extra fifteen feet to travel. The offence has not created a shooter. It has deleted a helper. That is a more direct attack on the coverage than any amount of shooting, and it is why the empty-side ball screen has become a default way to start a possession against a drop.

Then there is the trick of screening the screener's defender. If the big man is going to drop towards the rim, the offence can send a second screener to set a back screen on him as he retreats, which is the action usually known as a Spain pick and roll. The dropping big now has to negotiate a body while going backwards, while tracking a roller in front of him and a shooter behind him. The coverage has not been beaten by better execution, it has been made physically impossible to run. The same idea in a simpler form, a screen set on the screener's defender before the ball screen even happens, gets him moving early so that he arrives at his own coverage out of position.

None of this is decoration. Each of them is aimed at a specific defender's specific job, which is what separates a designed action from a good-looking one.

Mismatch hunting is what a switch buys, and what it costs

Switching is the coverage that concedes nothing immediately and something considerable eventually, and the shape of the eventual cost is worth spelling out because it is the most misunderstood part of the action.

After a switch, the offence has been handed a right it does not normally have: the right to choose the matchup. It exercises that right by screening until the pairing it wants appears, which may take two or three screens, and then attacking it. The two attacks are opposites. A guard now being guarded by a big man wants space and isolation, so the other four attackers clear out and he drives. A big man now being guarded by a guard wants the ball close to the rim, so he seals his smaller defender under the basket before the pass arrives, which is a race his teammate has to see coming.

The cost of hunting is time, and the defence knows it. Every re-screen burns three or four seconds. A defence that switches everything is quietly happy to trade fifteen seconds of shot clock for a contested shot against a mismatch, because a hunted mismatch attacked with six seconds left is a much worse possession than a four-on-three attacked with eighteen. Switching converts an immediate advantage into a delayed one, and delayed advantages are defendable.

The defence also has counters that do not require changing coverage. It can pre-switch, trading assignments before the screen arrives so that the screen produces the matchup the defence wanted rather than the one the offence was hunting. It can top-lock the intended screener, denying him the route to set the screen at all. And once a mismatch has happened, it can scram switch: a third defender, usually the one guarding the nearest non-threat, trades assignments with the small defender before the ball gets inside, so the mismatch is repaired without anybody ever double teaming. A defence that scrams well can switch everything and still never post up a guard, which is why the coverage survived contact with the era of the mismatch hunt.

The mismatch itself is also frequently overrated. A guard being posted by a much larger man is at a disadvantage; a guard who is strong, who fronts, who takes the space early and forces the entry pass to be lobbed, is a much smaller disadvantage than the television broadcast implies. What genuinely breaks a switching defence is not size, it is a large man who can handle the ball facing the basket, because he attacks the small defender in the one place the small defender cannot get help.

The best answer to the pick and roll is personnel, not scheme

Here is the conclusion that all of the above points at, and it is not a comfortable one for anybody selling tactical sophistication.

Every coverage is public. There are four of them, they have been known for decades, they are taught at every level of the sport, and no professional coaching staff is going to be surprised by any of them. There is no secret scheme. What varies between defences is not which coverage they choose. It is which coverages they are physically able to run.

Two abilities determine the whole menu.

The first is whether the on-ball defender can get over a screen and stay attached. A guard who fights over the top and arrives on the ball handler's hip a half step later has, by himself, cancelled the action, because the screener's defender never has to leave and the third defender never has to tag. Nothing else in the defensive scheme is required. That single skill, which is mostly footwork and willingness rather than athleticism, removes the whole problem before it starts.

The second is whether the big man can guard in space for four seconds. If he can, the defence can switch, which means it never has to help, which means its three off-ball defenders never leave three shooters. If he cannot, the defence must drop or blitz, and both of those have a price the offence gets to choose how to collect.

A defence that has both can run any coverage it likes and can change between them mid-possession. A defence missing one has a menu of three. A defence missing both is picking which way to lose, and the opponent will spend the entire night running screens at whichever of its players is the least equipped, because the offence gets to choose who is tested. Hunting the weakest defender is not a sophisticated tactic, it is just the obvious one, and it is available on every possession.

That is the real reason the market for large players who can move their feet on the perimeter is what it is, and it is also the logic behind going smaller to buy switchability, which trades rim protection for the ability to guard the action one-on-one. Both are the same purchase: they are attempts to buy the option of not having to answer the question at all.

The offence's side of the roster equation is a mirror image. A ball handler who shoots off the dribble beats a drop. A screener who passes beats a blitz. A screener who shoots beats a drop from the other direction. A screener with hands and size beats a switch, mostly on the offensive glass. There is no personnel combination that beats everything, which is why coverage selection is a matchup problem rather than a philosophy, and why the same coverage can be correct on Tuesday and indefensible on Thursday.

Watch one possession and name the coverage

The useful skill is not knowing the definitions. It is being able to say, out loud, within a second of the screen being set, which of the four answers the defence has chosen. It takes four observations, in this order, and none of them involves watching the ball.

Look at the screener's defender's feet at the moment of contact. Retreating towards the rim is a drop. Standing level with the screen and upright is a hedge about to happen. Above the screen with his hands up is a blitz. Sliding onto the ball handler's outside hip and staying there is a switch. Sitting back towards the baseline while the ball is pushed down the sideline is ice. That one glance identifies the coverage more reliably than anything else on the floor.

Look at the on-ball defender's route. Over the top means the defence intends to contest the jump shot. Underneath means it has decided to concede it. Jumping to the topside means the ball is being sent to the baseline on purpose.

Look at the weak-side corner defender's first step. This tells you what shot the possession is going to produce. If he steps into the paint, the corner is about to be open and the ball is going there. If he stays glued to his man, nobody is tagging and the roller has a clear run at the rim. The defence has already chosen; the offence only has to notice.

Then look at where the ball ends up compared to where it started. A shot taken by the same man who came off the screen, from roughly where the screen was set, was a drop that worked. A shot in the corner means somebody tagged. A shot at the rim by the screener means nobody did. A contested jump shot with four seconds left by a player who was not involved in the original action means the defence switched and the offence spent the whole clock hunting.

Do that for one game and the action stops looking like a play. It starts looking like what it is, which is a negotiation conducted at speed between two coaching staffs, in which the offence asks the same question every possession and the defence has to keep choosing which of five men it is prepared to abandon. The best offences are not the ones with the cleverest screens. They are the ones that notice the answer fastest. Everything else about the geometry of the professional game sits downstream of that one exchange.