BOSTON — Dwight Lowry and DeMar DeRozan, Toronto’s dynamite backcourt, caught fire in the second half and led the Raptors from behind to a 101-94 victory over the Boston Celtics on Friday night.

Lowry scored a season-high 34 points, 21 in the second half, and DeRozan added 24, 16 after halftime — a night after the guard combo had 52 points in a home win over the Minnesota Timberwolves. Lowry iced the game with five free throws in the final 30.6 seconds.

The win, in the second half of a back-to-back and Toronto’s eighth in the last nine games, came over a Celtics team that was playing its second straight game without top scorer Isaiah Thomas, out with a groin strain.

Norman Powell added 20 points, Jonas Valanicunas grabbed 10 rebounds and Patrick Patterson had 10 boards and four assists off the bench in the win.

Al Horford and Avery Bradley scored 19 points apiece for the Celtics, Horford adding seven rebounds and six assists, while Terry Rozier had 12 points off the bench.

The Celtics (13-10) fired up 42 3-pointers, making 17, and missed seven of their 22 free throws, while the Raptors (16-7) went 22-for-25 from the line, Lowry and DeRozan combined to go 18-for-19.

The Celtics, who led by 14 after Toronto’s six-minute drought in the first half, were ahead by 10 when Lowry scored 12 points in the last 5:14 of the third quarter. He started his run with a 4-point play and was also fouled on another 3-pointer, making all three free throws.

He and DeRozan combined for 24 points in the quarter and Powell scored his team’s first eight points of the fourth quarter. The visitors built their lead to 11 and led 89-78 with 6:12 left.

Horford made two free throws and set Bradley up for a 3-pointer to cut the Toronto lead to four with 2:56 remaining.

The Toronto lead was four when Horford was called for fouling Lowry on a 3-pointer as the 24-second clock was running out — and Lowry made all three free throws with 30.6 seconds remaining.

The Celtics led 32-21 after a Lowry basket with 9:56 left in the first half. By the time Lowry went 1-for-2 from the foul line with 4:17 remaining, the Celtics had run off 13 straight to take a 14-point lead.

Lowry scored six points in a 50-second burst and the Raptors wound up trailing by eight at the half.

The Celtics hit their first four 3-pointers and were 9-for-19 from behind the arc in the opening half.

NOTES: Celtics G Isaiah Thomas missed his second straight game with a groin strain but is officially day to day. He will accompany the team on its two-game road trip, but there is no slated return to action. Before the game, he reacted strongly to talk that the team played better without him in the win in Orlando and said he is making sure he’s healthy — at the team request — before he returns. … Toronto coach Dwane Casey didn’t like the way his team played defense in Thursday night’s win over the Minnesota Timberwolves and saluted the Celtics before the game. “There’s no question, they’re right there with us,” he said. “Talent-wise, they’re one of the most talented teams in the Eastern Conference, so we know who they are and what they are.” … Former Celtic Jared Sullinger still hasn’t played a game for the Raptors, his new team, because of foot surgery. … The Celtics visit Oklahoma City on Sunday. The Raptors, who just finished a six-game homestand, host the Milwaukee Bucks on Monday.

Cavs 114, Heat 84

CLEVELAND — LeBron James scored 27 points against his former team to move into ninth place on the NBA’s career scoring list in the Cleveland Cavaliers’ 114-84 victory over the Miami Heat on Friday night.

James added eight rebounds and eight assists, and Kevin Love fought through back spasms to contribute 28 points and 15 rebounds. Kyrie Irving scored 23 points.

Injuries and Dwyane Wade’s defection in free agency have reduced the Heat to smoldering ashes, last place in their division and little hope of making the playoffs.

Udonis Haslam was a late scratch for personal reasons, wiping away the final link between James and the Heat’s championship past. There was no one on the floor in a Miami jersey whom James played with — and he only left the franchise three seasons ago.

Former Cavs guard Dion Waiters (torn thigh muscle) was one of six injured Miami players unable to play. They began the game with just three subs, although they managed to hang around until the second half.

Irving’s driving layup at the third-quarter buzzer extended the Cavs’ lead to 87-69 and coach Tyronn Lue pulled his regulars after James passed Elvin Hayes (27,313) for ninth place on the scoring list.

Derrick Williams scored 18 points, Goran Dragic added 15 and Hassan Whiteside had eight points and 12 rebounds for the Heat, who dropped their fourth straight.

Miami shot a season-low 34.8 percent from the field, which is also the lowest percentage for any Cavs opponent this season.

The Heat’s starting frontcourt combined for 20 points, meaning Love and James each outscored them alone. Thompson grabbed eight rebounds for the Cavs and Iman Shumpert scored 10 points off the bench.