Returning after missing the last game with a bruised right leg, Irving had 10 points and six of his career-high 18 assist in the fourth quarter — including passes to set up Boston’s last three baskets in a game-ending 17-4 run.
Al Horford scored 24 and Jayson Tatum had 16 points with 10 rebounds for Boston, which returned home after losing three straight on the road.
Kawhi Leonard scored 33 points and Serge Ibaka had 22 with 10 rebounds for the Raptors, who had won five in a row heading into the matchup of two teams that consider themselves the heir to LeBron James’ Cavaliers as the best team in the East.
Toronto led 104-100 after Leonard’s three-point play with 4:22 left before Boston scored 17 of the next 19 points. Tatum had a three-point play and then a 3-pointer to give Boston a 106-104 lead, before Toronto tied it.
Irving then hit consecutive baskets, popping his jersey for the adoring crowd after connecting on the second from just a step or two inside the center tipoff circle. He then went to the pass, assisting on Boston’s last three baskets of the game before Toronto’s last bucket ended it.
After adding Leonard in the offseason, the Raptors have zoomed to the top of the conference standings. But despite getting Irving and Gordon Hayward back from injuries that kept them out of last year’s playoffs, when the team went to the conference finals, the Celtics have stumbled their way to the fifth-best record in the East.
Leonard scored nine in the first quarter, when the Raptors opened an 18-7 lead in the first five minutes. Boston cut it to six at the end of the first and then went on a 12-2 run early in the second to take the lead.
It was 46-44 with just over four minutes left in the half when the Celtics scored 11 of the next 13 points to open a double-digit lead. In all, Toronto scored just 17 points in the second, missing all nine 3-point attempts.
The Celtics made just one of their first 11 shots in the fourth, giving up nine straight points to trail 92-89 midway through the quarter. But Aron Baynes, who had made 12 3-pointers all season, hit one from the top of key to stop the run and tie it.
Baynes, who missed a month with a broken bone in his left hand, returned and played 14 minutes, scoring nine points with five rebounds. Irving and Smart also returned after missing Monday’s game in Brooklyn.
Bucks 111, Grizzlies 101
Eric Bledsoe added 16 points and D.J. Wilson scored 13 for the Bucks, who won for the 14th time in 17 games.
Omri Casspi led the Grizzlies with 17 points. Marc Gasol, Mike Conley and JaMychal Green scored 14 points apiece for Memphis, which lost its ninth in the last 10.
The Grizzlies took their only lead of the game at 59-58 early in the second half on a 3-pointer by Gasol.
Pistons 120, Magic 115 (ot)
Andre Drummond added 14 points and 21 rebounds for the Pistons, who won for the third time in 11 games. Detroit had six players with at least 13 points.
Nikola Vucevic and Terrence Ross each scored 24 points for Orlando, which had won two in a row after a four-game losing streak.