Celtics forward Jayson Tatum battles for a loose ball with San Antonio’s Keldon Johnson during Boston’s 143-140 overtime win Friday night at TD Garden. Elise Amendola/Associated Press

BOSTON — Even a few members of the Boston Celtics couldn’t quite believe they pulled off their latest comeback.

The Celtics turned around a woeful first half, storming back from a 32-point deficit and beating the San Antonio Spurs 143-140 in overtime on Friday night.

Jayson Tatum scored a career-high 60 points for the Celtics, including 21 in the fourth quarter and 10 more in OT, capping the improbable comeback with a pair of free throws with four seconds remaining.

“He did exactly what a great player is supposed to do,” Jaylen Brown said of Tatum, who reset his career-high twice in the month of April. “He was efficient, led us, hit timely shots – big baskets – real big-boy basketball. That’s what we need. We’re going to need that going forward.”

Brown finished with 17 points and hit a 3-pointer with 16.7 seconds left in OT that finally gave the Celtics the lead for good after the team had been booed off the court at halftime. Marcus Smart had 10 points and 12 assists, and Aaron Nesmith had 16 points and six rebounds for Boston.

“I think the best part was obviously coming back and winning and just seeing everybody contribute,” said Tatum, whose 60 points tied Larry Bird for the franchise scoring record. “That just kind of shows the growth of our team – to see everybody contributing when we’re down 30 points and just figuring out a way to win the game.

Tristan Thompson pulled down 15 rebounds and scored eight points for the Celtics, who moved a half-game up on Miami for sixth in the Eastern Conference standings.

“We haven’t been this bad very often. The first half, this was a different level,” Boston Coach Brad Stevens said. “We just have to stay in the moment and figure out how to be better for 48 minutes. That’s it. I’m proud of our resiliency, our resolve, our togetherness, our willingness to put aside whatever happened in the first half.”

San Antonio shot 71.4% in the first half, leading by as many as 32 points in the second quarter. The Spurs held a 31-point lead in the third before the Celtics started a furious rally that required an extra five minutes to complete.

DeMar DeRozan had 30 points and 14 assists for the Spurs. Dejounte Murray and Lonnie Walker IV finished with 24 points each, and Jakob Poeltl had with 15 points and 10 rebounds.

“We left the door open – too many opportunities,” DeRozan said.

Tatum’s previous career best was 53 points, which he scored against Minnesota on April 9. Tatum had 50 points at the end of regulation, just missing a jumper in the final seconds that could have prevented the overtime. The extra time gave him a chance to tie Bird’s record, set March 12, 1985, against Atlanta.

“It was something I never would have imagined at this stage,” Tatum said.

TIP-INS

Celtics: Tatum scored 14 of the Celtics’ 16 points in the first quarter. Thompson was the only other Boston player to score. … Guard Kemba Walker (left oblique strain) missed his third straight game. … Smart returned from a one-game suspension handed down by the NBA for “threatening language” he directed at a referee Tuesday night during Boston’s 119-115 loss to Oklahoma City.

Spurs: Murray hit his first nine shots and didn’t miss until midway through the third quarter. … Guard Derrick White (right ankle sprain) missed his third straight game. … Forward Trey Lyles was also out because of a right ankle sprain.