Al Horford has not been as impactful as usual to start this season. For the first time in his career, the veteran big man accepted a bench role among a talented roster. He has played fewer minutes. Through the Celtics’ first 10 games, he was slumping from 3-point range.

But with the Celtics shorthanded for the first time this season, they needed Horford – among others – to step up. The 37-year-old proceeded to turn back the clock again.

With Jaylen Brown and Kristaps Porzingis both out for the first time this season, Horford slid back into the starting lineup and had his best game of the season. Down two starters, Horford and the rest of his teammates stepped up. The Celtics received contributions from everywhere on the roster as they figured out a way to leave Philadelphia with a win, avenging last week’s loss to the 76ers with a 117-107 victory on Wednesday night.

Jayson Tatum led the way with 29 points as the Celtics won their fourth consecutive game. But it wouldn’t have been possible without huge plays around him. Derrick White had 27 points as he took over in the fourth quarter. Jrue Holiday made several plays with 18 points and 10 boards. The bench had big contributions. And of course, Horford’s huge night propelled the Celtics, which included four enormous 3-pointers and five massive blocks in the second half that pushed them over the top.

“It starts with Al. We can’t have the type of culture and the type of team and the thing we have without a guy like him,” C’s coach Joe Mazzulla told reporters in Philadelphia. “For him to come off the bench in some games and then when his name is called, to play the way he did in that second half.”

Horford was one of the best 3-point shooters in the league last season, but he’s started slow from deep this season. He was shooting 23.1 percent entering Wednesday. He hadn’t made more than two in a game. He actually missed his first three attempts on Wednesday, but Mazzulla told him to keep shooting.

He listened, and the Celtics reaped the benefits.

After another horrid second quarter in which the Celtics allowed 36 points, they came out firing in the third. Horford proceeded to make three triples in a span of two minutes as the C’s took the lead and control.

“When you can empower him and when he’s ready to go, it just makes us a different team,” Mazzulla said. “He’s on that list of like, when he plays hard, he inspires everybody.”

The C’s, behind strong non-Tatum minutes from the bench, took an eight-point lead into the fourth but the 76ers threatened. De’Anthony Melton’s 3-pointer cut Philly’s deficit to 89-88 with 8:41 left. Mazzulla thought about calling a timeout, but trusted White to run the show in that moment. White delivered again. He hit a triple against the zone, then he made a floater, and then he found Luke Kornet on a pick and roll, which led to a foul as the guard eased the C’s with his steady play.

White scored 14 of his 27 points in the fourth, and added three assists in the period as he helped the C’s hold off every Sixers run.

“He’s one of those guys that always shows up and makes the right play, and I thought he made some big-time plays,” Mazzulla said.

The Celtics still had not clinched the win though. The 76ers cut it back to 99-98 with less than six minutes to go, but the C’s made all the plays down the stretch. Tatum stripped Embiid before completing a three-point play the other way. On the next possession, Horford blocked a shot from Tyrese Maxey and then found White for a 3-pointer.

Embiid’s hook shot made it 107-102 with 2:51 left, but Horford responded with a 3-pointer from the corner to restore the Celtics’ lead to eight, and he had some words for some fans in the Philly crowd as he went back on defense. About a minute later, Horford posted his fifth block of the night on Robert Covington’s layup attempt before Tatum drilled a dagger 3-pointer.

Other takeaways and notes:

– Embiid was a game-time decision on the second night of Philly’s back-to-back with left hip soreness. He pushed through the injury to play but the Celtics’ defense did a good job on him again. Embiid had 20 points, nine rebounds and seven assists, but the C’s dominated the minutes he was on the floor. Embiid finished as a minus-25, the fourth-worst mark of his career.

– For the second consecutive game against the 76ers, the Celtics suffered from a disastrous second quarter. After building an early lead as large as 17, they let it all go by allowing 36 points to the 76ers thanks to several self-inflicted mistakes. The Celtics committed six turnovers in the period that led to 12 points for the Sixers, who took a one-point halftime lead.

– The Celtics’ bench shined in a huge first quarter. Dalano Banton was the first player off the bench and made an immediate impact. He had a putback layup, then made a steal of Embiid that led to a fast-break layup for Holiday. Eight different Celtics – including Svi Mykhailiuk – scored in a dominant first quarter as they used hustle plays and strong defense to take a 37-22 lead.

– Porzingis missed Wednesday’s game due to a right knee contusion, while Brown was out because of an illness. It’s unclear if they’ll return for Friday’s game in Toronto, but Porzingis told reporters in Philadelphia that he doesn’t believe his injury is serious.