BOSTON -- The way things are going for Isaiah Thomas, the last thing he needs is extra motivation.

Wednesday night, Boston's little big man had not one, but two sources of motivation that may or may not have led to his latest explosion that produced the Celtics' latest win.

"Honestly, Brad (coach Stevens) killed us at halftime," Thomas said after scoring 18 of his 44 points in the final 6:12 to propel the Celtics to a 109-104 victory over the Toronto Raptors -- Boston's fifth straight victory. "He yelled at us, that was probably the most mad I've seen him."

The Celtics trailed by 11 at the half and 18 in the third quarter before the fourth again belonged to Thomas -- who said after the game some words, that apparently were taken out of context because of a language barrier, by a Raptor urged him on.

"I remember when (Jonas) Valanciunas said we were trying to get for second (place) and they were going for first," Thomas said of a Valanciunas comment made after the last time the teams played. "It's the other way around now, they trying to chase for second and we're going for first. Words come back to bite you if you can't back it up."

Thomas hit a go-ahead 3-pointer with 48.1 seconds remaining and nailed it down with four free throws in the final seconds. He went 15 for 16 from the line and is 30 for 31 in the last two games, 39 for 40 in the last three.

The win, over a Toronto team playing the second half of a back-to-back without injured All-Star starter DeMar DeRozan, gave the Celtics (31-18) a 1 1/2-game lead over Toronto atop the Atlantic Division. It also gave Stevens the same lead over counterpart Dwane Casey in the chase to coach the Eastern Conference All-Stars.

The team ahead at the end of play Sunday's sends its coach to New Orleans.

It was also Boston's first win in three games against Toronto (30-20) this season.

"You know what's crazy is I thought we played better in the first two games," Stevens said.

Thomas, leading the NBA in fourth-quarter scoring at 10.3 points per game coming in, also had seven assists and four rebounds. The first two of those foul shots came after a big offensive rebound by Marcus Smart.

Thomas, who scored nine straight points in 1:33 to wipe out an eight-point deficit, won a fourth-quarter shootout with fellow All-Star Dwight Lowry. The Toronto guard had 12 of his 32 in the fourth for his fourth straight 30-point game.

"You gotta trap him, get the ball out of his hands," Lowry said of Thomas. "He got three wide open looks in the fourth. That can't happen."

Thomas was 4 of 7 from the field in the first half, but his 10 for 11 from the foul line gave him his 33rd straight 20-point game as he closes in on John Havlicek's club record of 40 set in 1971-72.

In the last 12 home games, Thomas has 440 points in 433 minutes. He is averaging 29.7 points this season.

Jae Crowder added 14 points and eight rebounds, Al Horford 11 points and six assists and Smart 10 points, five rebounds and five assists off the bench for the Celtics, who won without the injured Avery Bradley and Kelly Olynyk.

Former Celtic Jared Sullinger, making his TD Garden return, had a season-high 13 points and six rebounds in 15:37 off the bench. Norman Powell had 12 points and Patrick Patterson and Lucas Nogueira 10 apiece off the bench.

Ironically, Valanciunas, limited to 11:47 because of foul trouble, had only three points and three rebounds.

"It doesn't always come down to the fourth quarter," Casey said. "We missed a lot of free throws, a lot of mistakes in the first half even when we had the lead and those things add up and bite you in the behind going into the fourth quarter.

"But I thought our guys battled. I love the fight and scrap. We got to continue that, get everybody healthy, get guys off of minute restrictions and we'll go to war. But I like our fight ... we came up a little short and missed some shots we normally make."

The Raptors, 8-10 since the start of January, went 14 for 25 from the foul line.

NOTES: Both teams were missing starting guards, with DeMar DeRozan out for the fifth time in the last six Toronto games with an ankle sprain. Boston's Avery Bradley missed his eighth straight with an Achilles tendon strain and is considered day-to-day. ... F Kelly Olynyk (shoulder) was also out for Boston as a late scratch. ... The Raptors are at Orlando on Friday and Brooklyn on Sunday, while the Celtics host the two Los Angeles teams -- the Lakers on Friday and Clippers on Sunday.