A season built around restrictions
The tenth Big Bash League was played between 10 December 2020 and 6 February 2021, in the middle of the COVID-19 pandemic. State border closures meant fixtures were moved at short notice, several clubs spent long periods away from home, crowds were capped, and much of the finals series was played at Manuka Oval in Canberra rather than at the grounds of the qualifying sides. Attendances were a fraction of the previous season's.
Cricket Australia used the same summer to change the rules. Three innovations were introduced: the Power Surge, a two-over batting powerplay that the batting side could take at any point after the eleventh over; the X-Factor player, a substitute who could replace a player who had not batted or had bowled no more than an over, available after ten overs of the first innings; and the Bash Boost, a bonus point awarded to whichever side was ahead of the other's ten-over score at the halfway point of the chase. Wins were worth three points and the Bash Boost one, so a team could take two points from a defeat.
The league stage
Sydney Sixers finished first with nine wins and nine Bash Boost points. Perth Scorchers were second, Sydney Thunder third, and Brisbane Heat and Adelaide Strikers took the remaining places ahead of Hobart Hurricanes, who had the same seven wins. Melbourne Renegades, champions two years earlier, won four and finished last for the second successive season.
On 13 December the Sixers bowled the Renegades out for 60 at Blundstone Arena and won by 145 runs, the largest margin in the competition to that point. Alex Hales made 543 runs for Sydney Thunder, more than anyone, including 110 in a total of 232 for 5. Jhye Richardson took 29 wickets for Perth. Josh Philippe, the Sixers' wicketkeeper, was named player of the tournament.
The finals
Brisbane Heat beat Adelaide Strikers in the Eliminator at the Gabba and then Sydney Thunder in the Knockout at Manuka Oval, both by comfortable margins. Sydney Sixers beat Perth Scorchers by nine wickets in the Qualifier, James Vince making an unbeaten fifty, which put the Sixers into the final and Perth into the Challenger. There Perth made 189 for 1 in a rain-shortened 18.1 overs and beat Brisbane by 49 runs on the Duckworth-Lewis-Stern method, Liam Livingstone taking the award.
The final
The final was played at the Sydney Cricket Ground on 6 February. Sydney Sixers made 188 for 6 and held Perth to 161 for 9. James Vince was named player of the match for the second time in the finals series. It was the Sixers' third title and their second in succession, making them only the second club after Perth Scorchers to retain the trophy.
What survived
The Power Surge and the X-Factor player remained in the competition. The Bash Boost point was dropped after two seasons, having been widely criticised for rewarding sides that lost.