Boston Celtics big man Robert Williams III was ruled out with left knee soreness Saturday before the start of Game 3 against the Miami Heat.
He was added to the injury report earlier in the day.
Daniel Theis started in place of Williams with the series split after the first two games.
Williams played in the first two games of the best-of-seven Eastern Conference finals after a four-game absence due to issues with his left knee.
He contributed 18 points, nine rebounds and two blocked shots in 28 minutes in the Game 1 loss, but had just five points, four rebounds and three blocks in 20 minutes in the Game 2 victory.
Also, both Kyle Lowry (left hamstring) and forward P.J. Tucker (left knee) were healthy enough to start for the Heat on Saturday. Miami coach Erik Spoelstra had said previously that both players would go through their pregame routines before deciding if they could play.
--Field Level Media