Watch: Celtics coach tries to block Suns player after whistle

After a Jaylen Brown dunk gave Boston an 18-point lead with 2:58 to go, Phoenix called timeout to wave the white flag and pull their starters. Royce O'Neale, who was 0 for 7 and heading to the bench, put up a shot after the timeout was called. And Mazzulla, a former West Virginia guard, leaped to contest the meaningless shot.

Mazzulla explained that because he asks the players not to let a player see a shot go in, even when the ball is dead, he and his staff need to be willing to do that as well.

While it's rare to see an NBA head coach get involved in on-court action like this, it's not at all surprising to see someone from the Boston Celtics do it. Denying all post-whistle shots was a trademark of former Celtic Kevin Garnett, who made it a personal mission to block or goaltend any and all shots after the whistle.

Mazzulla may not have been the player Garnett was, but he has similar intensity. Last year, Mazzulla missed two games with an eye injury suffered when a pickup game at TD Garden got rough. 

One would guess he doesn't tolerate shots after the whistle in those games either.