PHILADELPHIA — The chants of “TJ! TJ!” grew louder each time T.J. McConnell darted through the lane for an easy basket or buried a 3-pointer to build an insurmountable lead Monday night for the Philadelphia 76ers.

He wore a sheepish look as teammates rubbed his head on the bench in appreciation, the big moment for an undrafted guard who plugged a role in the early Process days and morphed into a surprise postseason savior.

McConnell turned an eye-popping start into the save of the season and Dario Saric scored 25 points to help Philadelphia stave off elimination in a 103-92 victory against the Boston Celtics in Game 4.

“If I saw a lane, I took it. If I had an open shot, I would try and take it,” McConnell said.

Easy enough.

Yet the Sixers still face daunting odds headed into Game 5 and trailing 3-1 in the Eastern Conference semifinals: No NBA team has won a series down 3-0.

McConnell had a career-high 19 points, seven rebounds and five assists in his second start of the season, and meshed well in the backcourt with Ben Simmons. The crowd chanted his initials each time he touched the ball in the fourth quarter and he proved why he has been so valuable even as bigger stars sliced his playing time.

He was just what Coach Brett Brown, the South Portland native, needed in a must-win game.

“I can tell you the Philadelphia 76ers’ spirit is just fine,” Brown said.

With NBA teams down 3-0 having lost all 129 series, the Sixers may need more than spirit to pull off this stunner.

Joel Embiid had 15 points and 13 rebounds, and Simmons added 19 points and 13 boards.

Jayson Tatum led the Celtics with 20 points. Marcus Morris had 17.

The Sixers spent the second half in control in what could be their last home game of the season.

Embiid was still in the mix in his mask, stirring it up with any Celtic within his wingspan. He chirped at Marcus Morris in the third quarter and Morris flashed a “3-0” with his hands. McConnell buried a 3 for a 14-point lead that would soon make that combination obsolete.

“It was a pretty special moment,” McConnell said of the chants. “I think we have the best fans in the NBA. They’ve been here through the dark times and they’ve certainly been here on our rise.”

So has McConnell.

With a chance to shine, he zipped inside for easy buckets, made the extra pass to keep the offense rolling and made dives for loose balls.

“How do I help my stars be stars because at the end of the day that’s what we need,” Brown said. “That’s my job.”

The anticipation of elimination and a 6 p.m. tip sharply cut into attendance and the game had more of an early-season feel until Embiid and Terry Rozier shook everyone up with pushing and shoving late in the first half. Embiid tried to strip the ball from Rozier after the whistle. Rozier tightened his grip and Embiid slapped at the ball again. The 6-foot-1 Rozier shoved the 7-2 Embiid in the chest with his right hand and the two quickly had to be separated.

“He tried to punch me twice. Too bad he’s so short he couldn’t get to my face,” Embiid said.

Rozier and Embiid were hit with technicals. Then they each hit 3s.

The Celtics took a punch but they can still finish it Wednesday at home.

“Finish the game. Get it done,” Jaylen Brown of Boston said. “Advance and do what we were supposed to do.”

NOTES: The Celtics could be even more of a threat had Kyrie Irving and Gordon Hayward not been lost this season to injury. “There’s not a coach in the world that wouldn’t want everybody available,” Coach Brad Stevens said. “I think that obviously we’d be better with those guys. They’re very good players. Both unselfish players. But I really like this group and those guys are still a part of that.” …Celtics guard Shane Larkin left with a left shoulder injury in the first quarter. … Markieff Morris of the Wizards was in the stands to support his twin brother, Marcus. The brothers are Philadelphia natives. … The Sixers scrapped their confetti cannon celebration after it was prematurely shot off in Game 3.