Preseason basketball is usually low stakes. There’s no bad blood, just clean reps before the regular season starts. But tonight, inside TD Garden, the tone is far from casual. From the opening tip, Celtics vs Raptors has been a back-and-forth competition, with loud benches and physical play, culminating in a confrontation between Celtics head coach Joe Mazzulla and Raptors guard Immanuel Quickley that no one saw coming.

After hitting a shot in the first half, Quickley turned to the Celtics bench, making a ‘call #5’ motion, taunting them with his shot-making as the Boston coaches called a timeout. Seconds later, Joe Mazzulla turned to the smirking Quickley and shouted at him: “Shut the f— up.” Cameras caught the outburst, and the exchange was replayed on the Toronto broadcast, announcers laughing.

The clip quickly circulated on social media. Mazulla stepped onto the floor slowly while yelling at Quickley, his assistants motioning him back. Quickley, however, didn’t seem bothered as he returned to his team’s huddle. This shouldn’t surprise Celtics fans, who have previously seen their coach display raw emotion on the sidelines.

Mazzulla has built a reputation for himself with a fiery sideline presence, and it helps drive Boston’s defensive mindset while building focus and culture. He’s barked at referees, challenged stars during huddles, and even jawed at opposing players. Once, he contested a shot from the Suns’ Royce O’Neale after the buzzer went off, and later said, “I saw a guy going in to try to get a shot, and he hadn’t made one, and I didn’t want him to feel good about himself going to the bench.”

On the other side, Quickley has never backed down easily. After arriving in Toronto midseason during the 2023-24 season, he played with a chip on his shoulder to prove himself more than a bench scorer. After a disappointing 2024-25 season, Quickley is looking to bounce back with a healthier season as the starting point guard for the Raptors. His energy and, at times, taunting make him dangerous, but can light a fuse under the wrong opponent.

A Familiar Flashpoint in a Growing Rivalry For Joe Mazzulla

This isn’t the first time Joe Mazzulla has found himself in a heated moment against Toronto. During a matchup against the two teams in April 2023, then-Raptors forward Chris Boucher bumped Mazzulla on the way back into his team’s huddle, immediately causing Mazzulla to start barking at the player. Coach was so heated that the Celtics’ big man, Robert Williams III, had to restrain him.

In an odd turn of events, Boucher, the longtime Raptor, has joined the Celtics and confirmed that the incident was one of the first things they discussed.

“He was like, ‘I remember when you bumped me. And I didn’t know where he was taking it from, but he said that’s like the type of guy that he likes. He wants the guys (who are) like, ‘It’s us against everybody,’ and I think that it is just like a mentality that I have, and I think Joe has it too,” Boucher said.

Both Mazzulla and Boucher also stated during Media Day that, looking back, they wouldn’t change how they approached the situation. Mazulla said, “It’s a classic hold-me-back moment.” Boucher stated that it would’ve “gotten real” and that, “I probably would do that again and again and again. I mean, it’s just who I am.“