TORONTO — Rookie guard Marcus Smart’s buzzer beating tip-in lifted the Boston Celtics to a dramatic 117-116 overtime victory over the Toronto Raptors on Saturday night.

Smart finished with 15 points but none were bigger than when he grabbed the rebound of a missed layup by guard Isaiah Thomas on a shot that was blocked by Toronto. After getting the rebound, Smart barely beat the buzzer with his biggest basket of the night.

Smart’s dramatic play came after Boston coach Brad Stevens called a timeout with 2.6 seconds remaining. It also came after guard Lou Williams hit a 3-pointer that gave Toronto a 116-115 lead with four seconds remaining.

Smart’s game-winning play was one of two big shots he hit in the extra session. Before Williams hit the 3-pointer, Smart had a corner 3-pointer that gave the Celtics a 114-113 edge with 32 seconds left.

Thomas scored 25 points and center Tyler Zeller added 20 points for Boston (35-42), which moved ahead of the Miami Heat into eighth place in the Eastern Conference. The Celtics are a half-game behind the Brooklyn Nets, who lost at Atlanta Saturday.

Guard DeMar DeRozan scored 38 points and Williams added 27 for Toronto, which lost a second straight game in the final minute in as many nights. On Friday, the Raptors were beaten in Brooklyn on a tip-in by Thaddeus Young with 22 seconds remaining in regulation.

Toronto rallied from an eight-point deficit and forced overtime on DeRozan’s five-foot jumper with six seconds remaining that forged a 104-104 tie. The Celtics had a chance to win in regulation but Thomas missed a 3-pointer at the buzzer.

NOTES: Raptors F Amir Johnson sustained a right ankle sprain after coming down on teammate Jonas Valanciunas’ foot in Friday’s loss to the Brooklyn Nets. F Tyler Hansbrough replaced Johnson in the starting lineup. … Toronto G Kyle Lowry (back spasms) missed his sixth straight game. … Celtics F Jae Crowder, who twisted his ankle in Friday’s loss to the Milwaukee Bucks on Friday, was active. … Boston F Jared Sullinger played in his second straight game Saturday after missing 24 games because of a broken foot. He was scoreless in 12 minutes. … Celtics’ G Isaiah Thomas scored 25 points Saturday and it was his highest total since returning from a back injury on March 25.