TORONTO - Toronto Raptors coach Dwane Casey told reporters just minutes before tipoff Saturday night that when his team finally had its edge back, everyone would know.

"You'll see it. Everybody will see it. It's that obvious," Casey said — perhaps sensing the end of the slump.

Turns out, Casey was right. Everybody saw it Saturday night in a dominant 109-96 victory over the Boston Celtics that saw Toronto's four-game losing skid come to an end, and the Raptors play with more energy — especially on the defensive end — than they've shown in weeks.

"I thought our defensive mojo was back," Casey said after the win. "I saw guys moving their feet, cracking down, rebounding, doing the things we needed to do with activity and anticipation."

Kyle Lowry scored 10 of his 19 points in the fourth quarter, Lou Williams also had 19 points, while James Johnson, Amir Johnson, and Jonas Valanciunas finished with 15 apiece for Toronto (25-11). Patrick Patterson finished with 10 points.

"I think we just got more defensive-minded and we really weren't worried about the offensive end," Lowry said. "We knew shots would fall. I think we put a real emphasis on defence tonight."

Kelly Olynyk of Kamloops, B.C., had 23 points — his best-ever performance in Toronto — 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 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.

Casey shook up the lineup, reinserting the athletic and hardworking James Johnson into the starting five.

"He covers up a lot of mistakes. He covers a lot of floor, a lot of ground. His effort has been unbelievable this season and we need him to keep it up," Lowry said of Johnson. "We love his energy, we love his enthusiastic nature and what he brings to the table."

The Raptors got off to another sluggish start, but picked it up in the second quarter, and broke the game open in the third. Lowry's step-back jumper with just under three minutes to play in the third capped a 23-6 run that put Toronto up by 15 points, brought the capacity crowd of 19,800 out of their seats, and breathed some life back into the Air Canada Centre.

"We were tired of it," James Johnson said, of the change in momentum. "Everybody buckled in. Everybody took responsibility for what they were doing and we started playing Toronto Raptors defence."

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's pre-game talk with reporters was dominated by the Raptors' funk. He said they badley needed to break out of it, but added that it's something that every team goes through at some point in a season.

"I'm watching the games (Friday) 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."

DeMar DeRozan's absence certainly hasn't helped the Raptors, who played their 20th game without him Saturday. 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.

"Canada basketball is huge up here. . .," Olynyk said afterward. "It's always nice to come up here and play well in front of your country."

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.

"They're at a different level than we are right now and we need to look at them as a team that we can learn a lot from," Boston coach Brad Stevens said of Toronto.

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.