Jason Terry scored Boston's last nine points and the Celtics weathered a strong comeback by the New York Knicks, avoiding a sweep with a 97-90 overtime win on Sunday.
Paul Pierce led the Celtics with 29 points as they forced a fifth game in the series, but it was Terry who provided the finishing touches.
In Game 3, he had been elbowed by J.R. Smith, and the NBA suspended the Knicks guard for Sunday's game.
New York had tied the game 84-84 after trailing by 20 points early in the third quarter. It was 88-all before the Celtics regained control and took the lead for good on a 3-pointer by Terry. Carmelo Anthony, who led the Knicks with 36 points, hit a short jumper, but Terry connected on a 15-footer with 50 seconds remaining for a 93-90 lead.
After Anthony missed a 3-pointer with 21 seconds to go, Terry was fouled and sank both free throws. He added a layup to close out the game.