“It felt good,” Tatum said. “It felt good to finally hit one. After the horrible miss I had at the end of regulation, it obviously felt good to bounce back.

The Raptors had a chance to take the lead with the score tied at 123, but Neemias Queta knocked away RJ Barrett’s layup attempt and gobbled up a rebound. After a timeout, Tatum held the ball near the right arc with his back to the basket and waited for the action to materialize.

But as Jaylen Brown curled off a screen to the top of the key, he was bumped by Davion Mitchell and flew across the field. Tatum paused for a moment, thinking there would be a false signal, but it never happened. As his other reading evaporated, he glanced at the clock on the other side of the floor and realized he would have to do this himself.

He had little luck creating space against Ochai Agbaji with jabs and shimmies, eventually sliding back and launching the deep 3-pointer over the Raptors forward’s outstretched arm. Al Horford said he’s seen Tatum work on this shot in practice this season, and right now that practice has paid off.

After the ball slipped through the net, Tatum walked backwards to the other side of the court before his teammates showered him with hugs and chest bumps. Even Horford’s young son, Ean, joined in the celebration.

“I play too much basketball to doubt the next shot,” Tatum said. “Whether it’s the in-and-out miss or the one that misses the rim, I know what I’m capable of.”

The Celtics were hopeful that Wednesday’s romp against the Nets would help them emerge from a period of uneven play. The arrival of Toronto, who entered Saturday with the NBA’s worst record and a roster decimated by injuries, made it easy enough to maintain that momentum.

Instead, the Celtics staggered through another imperfect performance before ultimately finding a way, with Tatum’s big shot ensuring the teachable moment wouldn’t also include another puzzling loss.

“We’re having success,” Horford said. “We probably won’t win the way we’re expected to, but the important thing is that we find ways to make it happen.”

Coach Joe Mazzulla acknowledged that some minor shortcomings have emerged, but he does not find them concerning as he believes they are not related to his team’s effort level.

“We are competing,” he said. “We’re just not performing at the level we need to. So there’s a difference… If you can win and you’re still in games, you’re not at your best, that gives you the mentality that you can get better.”

Brown had 27 points to lead the Celtics. Tatum finished with 24 points, 11 rebounds and 9 assists.

Raptors center Jakob Poeltl scored a career-high 35 points and led another dominant interior performance from a Celtics opponent. The Raptors had a 76-42 advantage in points in the paint. On the face of it, it’s a surprising number, but Mazzulla pushed back against the idea that his team was being hammered domestically.

He pointed out that Poeltl mainly dominated with mid-range push shots that had more finesse than physicality. For the most part, they were the shots Boston wanted Toronto’s big man to make. But they were also the photos he felt quite comfortable with, and this evening almost all of them went in.

“But he’s a bear down there,” Mazzulla said. ‘He’s good. You play one cover and he’s going to shoot it. If you play someone else, he’s going to bury you on the glass.”

A Horford 3-pointer with 1:45 left in regulation gave Boston a 112-110 lead, but Gradey Dick tied the score with a 16-foot pull-up and Barrett made it 114-112 when he scored inside when he was fouled. 59.2 seconds to go. But then Barrett missed his fourth foul shot of the quarter, and at the other end a Queta layup tied the score at 114 with 42.5 seconds to play.

Poeltl lost his position on Toronto’s last possession of regulation. Tatum then got a break when Agbaji fell, leaving him wide open at the top of the key but missing his clean look.

Neither team led by more than 3 points in the extra session, partly due to shot making, but mainly because the teams took turns missing opportunities. After a Brown 3-pointer with 1:09 left gave Boston a 123-121 lead, Barrett answered with a layup to tie the score, but Tatum would ultimately take care of the rest.

“It’s definitely worth coming out of a game like this,” Tatum said, “and knowing that you got it.”

Adam Himmelsbach can be reached at [email protected]. Follow him @adamhimmelsbach.