Before the Celtics faced the 76ers on Tuesday, Kyrie Irving bounded into the locker room with a message for his teammates. He told them more than 20 friends and family members were at TD Garden, and he had every intention of putting on a show for them.
“So I’m acting up,” Irving recalled saying. “Like, you guys have no idea. I’m so excited.”
Irving said it was unusual to have so many people he loved together in one place, and he wanted to make the most of it. And with 12.1 seconds left in overtime, he went to the bench and received a rousing ovation. For the first time in the night, his team did not need him anymore.
The All-Star point guard had 40 points and 10 rebounds and hit two critical 3-pointers in the final two minutes, as Boston came back from a 5-point overtime deficit and took a 121-114 win.
The Celtics, who closed the game on a 13-1 run, are 4-0 in overtime games this season.
“I wanted to have fun, enjoy being out there with my teammates,” said Irving, who had never reached the 40-point, 10-rebound marks in the same game before. “High-level game. I always talk about being on those big stages — it’s just so much fun. It’s competition at its highest.”
This win was the latest surge in this mercurial start to the season. Boston’s eight-game winning streak was followed by a three-game losing streak that sparked a pair of private team meetings over two days.
Now the Celtics have collected consecutive victories against the Hornets and 76ers, and, most important, they have done it with almost a fully healthy roster. Marcus Morris and Jayson Tatum finished with 23 points apiece to complement Irving’s explosion.
Al Horford played in his second consecutive game after missing seven in a row due to knee soreness. Although Horford did not have a sparkling offensive game — he was 2 for 10 and missed all five of his 3-point attempts — he was a critical piece defending Sixers big man Joel Embiid, who had spent much of the night feasting inside.
Embiid had 30 points through the first three quarters but managed just 4 points on 1-for-4 shooting in the fourth quarter and overtime, much of which he spent matched up against Horford.
Horford had entered the night with a 25-minute restriction, but he breezed past that after the game went to overtime and Brad Stevens received clearance from the medical staff to use him more.
“There was no question that I was going to play,” said Horford, who played 30 minutes, 28 seconds. “The game’s so emotional; we are right there. It just feels good to be able to finish out the game, no issues for me physically, and to be able to get the win.”
Embiid finished with 34 points and 16 rebounds, but he did not attempt a shot in overtime.
Tuesday’s game was a rematch of last season’s Eastern Conference semifinals that the Celtics won in five games. Philadelphia’s roster has been reshaped dramatically since then, though, most notably by the addition of the All-Star forward Jimmy Butler, who was still in Minnesota when these teams met on opening night.
Butler gives the 76ers yet another tough, physical player who is capable of taking over a game, and the alteration was obvious to the Celtics afterward.
“Obviously those guys have gotten better and it’s definitely tougher,” Horford said. “No question.”
The Celtics needed to craft a pair of mild comebacks to secure this win, and both were keyed by Irving. They trailed, 98-91, with just more than 8 minutes left in regulation before clawing back.
Irving converted a tough, driving layup with 1:29 left that gave the Celtics a 106-105 lead. With the shot clock running down, Embiid’s 3-pointer from the corner was long, and Wilson Chandler gathered the offensive rebound. But his putback attempt was emphatically swatted away by Jayson Tatum (23 points).
At the other end, Irving missed a tough layup and Chandler then gave the Sixers a 2-point lead by hitting an open 3-pointer with 36 seconds left. After a timeout, Irving danced around with the ball and finally rolled in a tough fadeaway over Butler with 19.7 seconds left.
“I just couldn’t get my hand underneath the basketball,” Irving said. “Jimmy was pressuring me so well. I was just trying to get to a spot and raise up over him.”
J.J. Redick’s jumper before the buzzer rimmed out, sending the game to overtime.
The Sixers scored the first 5 points of the extra session, including one after Marcus Smart received a technical foul for shoving Ben Simmons going for a rebound.
But Tatum threw down a dunk and then fed Gordon Hayward for an alley-oop layup. Then after Simmons made one of two free throws to give his team a 114-112 lead, Irving took control.
He hit a 3-pointer from the top of the key with 2 minutes left, and after Redick missed a 3-pointer, Irving raced the other way and pulled up for a deep 3, stretching the lead to 118-114. The 76ers would not score again.
“I’m about used to it now,” Marcus Morris said of Irving’s heroics. “When he first came, it was crazy. But some of the [stuff] don’t even surprise me no more with how often he does it, you know what I’m saying?”
Adam Himmelsbach can be reached at adam.himmelsbach @globe.com. Follow him on Twitter @adamhimmelsbach.