TORONTO -- Kyle Lowry scored 10 of 19 points in the fourth quarter to lead Toronto to a 109-96 victory over the Boston Celtics on Saturday, lifting the Raptors out of their four-game funk.

Lou Williams added 19 points, while James Johnson, Amir Johnson, and Jonas Valanciunas finished with 15 apiece for Toronto (25-11). Patrick Patterson finished with 10 points.

Kelly Olynyk of Kamloops, B.C., had 23 points to top the Celtics (12-23), while Avery Bradley added 17.

The Raptors had been mired in their worst slump in over a year, losers of four straight and five of their previous seven games before Saturday. Prior to this cold spell, they hadn't lost more than two in a row this season.

Coach Dwane Casey, perhaps sensing an end to their funk, told reporters before tipoff that everyone would know when his team had its edge back.

"You'll see it. Everybody will see it. It's that obvious," Casey said.

That moment seemingly came in the third quarter of a game that saw the Raptors get off to another sluggish start, but pick it up through the second and third quarters. A step back jumper from Lowry capped a 23-6 Raptors run that put Toronto up by 15 points and brought the capacity crowd of 19,800 at the Air Canada Centre out of their seats.

The Raptors, who were playing Game 2 of a six-game homestand, took an 82-65 lead into the fourth, and back-to-back three-pointers by Lowry, Amir Johnson, then Lowry again, gave them a 100-80 lead with 5:29 to play.

The Celtics responded with threes from Olynyk and Jared Sullinger to cut Toronto's lead to 12 points, but that was as close as Boston would come.

Casey said every team goes through a funk at some point of the season.

"I'm watching the games last night, and there are teams that look like they're playing in mud. They're trying. They're running. Their arms are flailing. But they're just not going anywhere. In an 82-game season, you have stretches," Casey said. "But you go through that. Every year I've been in the league I've gone through it."

The Raptors played their 20th game without DeMar DeRozan. The all-star had targeted this week for his return, but he and the team are playing it safe rather than taking any risks by rushing him back. DeRozan said he's looking to play "some time next week."

It was a strong performance in what was a homecoming of sorts for Olynyk. He was born in Toronto, where his mom Arlene was a scorekeeper for the Raptors and his dad Ken was the head basketball coach at the University of Toronto. The family moved to Kamloops when he was 12.

The rebuilding Celtics were playing the day after sending Brandan Wright to Phoenix in a trade for a protected first-round draft pick. Wright came to Boston in the Dec. 18 trade that sent guard Rajon Rondo to Dallas.

The Raptors got off to yet another woeful start -- the ninth time in 11 games they've been outscored in the first quarter. A running layup by Olynyk put the Celtics up by nine midway through the frame, and they led 26-19 going into the second.

Toronto used a 12-0 run in the second to take a three-point lead with a minute-and-a-half to play in the first half. Williams finished off a steal and pass from Patterson with a slam dunk to send the Raptors into halftime with a 47-43 lead.

The Raptors kept their foot on the gas in the third, outscoring the Celtics 35-22 in the quarter to lead by 17 at the end of the period.

Toronto hosts Detroit on Monday, then Philadelphia, and Eastern Conference-leading Atlanta, before capping its homestand Jan. 18 versus New Orleans.