BOSTON -- About an hour before Isaiah Thomas worked some of his now-familiar fourth-quarter magic, Boston Celtics coach Brad Stevens did something unusual: He tore into his team at halftime of Wednesday's game against the Toronto Raptors, angrily questioning their intensity during a key Eastern Conference matchup.

"Honestly, I mean, Brad killed us at halftime," said Thomas, who continued his absurd run of fourth-quarter heroics by scoring 19 of his game-high 44 points in the final frame as Boston rallied from an 18-point deficit to stun the Raptors 109-104 at TD Garden.

"[Stevens] yelled at us," Thomas added. "It was probably the most mad I've seen him. [Veteran Gerald Green] doesn't shut up, so he was also talking and saying some words we needed to hear. We still didn't come out like we wanted to in the third quarter, but with that in the back of our head I think that changed the game for us. We just played harder than them. We got the 50/50 balls and I think that was the deciding factor in the game."

Because Boston's 40-year-old coach controls his emotions so well, "Mad Brad" is a bit of a phenomenon in these parts. A Stevens technical foul lights up Twitter; so much as a scowl becomes a well-circulated GIF on social media.

This isn't the first time Stevens has blasted his team at halftime. During Boston's finale last season, the Celtics came out lethargic against the Miami Heat in a game that not only had playoff-seeding implications but featured members of three decades' worth of Celtics title teams ringing the court. Stevens essentially suggested that the Celtics were embarrassing themselves in front of the Boston legends, and his players responded by rallying from a 26-point deficit to win.

Maybe sensing that Wednesday's game will have an impact on the Eastern Conference standings down the road -- or maybe recognizing that his team simply needed to get over the mental hurdle and beat a Toronto team that has owned Boston in recent seasons -- Stevens raised some hell in the locker room.

Thomas was asked if Stevens might have even used some R-rated language.

"I'm not going to tell on the guy," Thomas said with a smile. "I don't know what he said. I don't know if he wants to put that out there."

Added teammate Jae Crowder: "[Stevens] was pretty upset. We weren’t playing with enough fight, enough energy. Those guys played last night and came out with more energy than us, so that was unacceptable."

Isaiah Thomas scored 19 of his 44 points in the fourth quarter to rally the Celtics. Maddie Meyer/Getty Images

The Raptors led by 11 at halftime and by as much as 18 with little more than 20 minutes to play. Boston managed to trim its deficit a bit late in the third quarter -- Jaylen Brown getting hot at a rather harmless Kyle Lowry foul breathed some life into the team -- and then Thomas, the league's top fourth-quarter scorer, did his thing.

Thomas scored his 19 fourth-quarter points on 6-of-10 shooting and was plus-16 over the final 10 minutes, 25 seconds. With Boston down eight with 6:22 to play, Thomas scored nine straight points over a 92-second span to push the Celtics out front. Thomas' 3-pointer with 48.1 seconds to play gave Boston a lead it wouldn't relinquish.

But because these sorts of outbursts are expected of Thomas, it was Stevens' outburst that really registered with Boston players.

"Very unusual," said guard Marcus Smart, whose hustle plays down the stretch, including winning a key jump ball, helped Boston find a way to win. "I think everybody knows Brad is one of the most calmer dudes you’ll meet, so usually when he’s fired up and he gets into us, it’s for a great reason."

Green, 31, the oldest player on Boston's roster, has embraced being a veteran voice in his second stint with the team that drafted him as a teenager. He spoke his mind before Stevens' arrival and then watched the typically stoic coach add his two cents.

"[Stevens] was hot, because this was a very important game," Green said. "That’s all we could talk about was how important this game was. I know this is a team we’ll need to see down the [road]."

Green added: "Honestly, today I just thought we were too loose. It’s OK to be loose. Sometimes when you play uptight you make more mistakes than others, but today we were too loose. I don’t want to get into details -- nothing out of the ordinary, but we were too loose today. I had a feeling it was going to be like that and I just got really mad. Coach -- said the same thing."

Green might not have a major rotation role, but his voice resonates on a young roster.

"I just had to let guys know," Green said. "I just thought we were better than that, better than how we came out. Sometimes coaches tell us that we have to pick our energy up and guys know the importance of us starting off good and how big this game was today. I thought we just started off flat. But those guys played tremendous in the second half, and that’s something that’s a learning process happening for us."

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With Wednesday's win, the Celtics now own a 1.5-game lead over the Raptors. If the Celtics have a better record after Sunday's game, Stevens and his staff will coach the Eastern Conference squad at All-Star Weekend in New Orleans. (East-leading Cleveland is ineligible after Tyronn Lue coached last season's game.)

Stevens has downplayed the honor but admits it would be a nice reflection of how well his team has played since mid-December. That the Raptors have hit a midseason funk hasn't hurt, either. But having finally defeated Toronto -- albeit with DeMar DeRozan sidelined (though Boston was missing Avery Bradley and Kelly Olynyk) -- the Celtics were able to celebrate owning the No. 2 spot and sitting just 2.5 games back of Cleveland for the top spot in the East.

"I remember when [Toronto big man Jonas] Valanciunas said we were trying to get to second and they were going for first," Thomas said. "So it’s the other way around now. They’re trying to chase for second. Now we’re going for first. So words come back to bite you if you can’t back it up."