BOSTON — Marcus Smart scored 20 of his 22 points in the second half, and the Boston Celtics beat the Oklahoma City Thunder 126-122 on Monday night for their seventh straight win.

Boston trailed by as many as 15 in the third quarter, but it outscored Oklahoma City 37-26 in the fourth.

“Tonight was a resilient win — a tough game to win,” said Jaylen Brown, who scored 26 for Boston.

Jayson Tatum had 27 points and 10 rebounds for the Celtics, and Al Horford added 12 points and 11 boards. Smart also had eight assists and five rebounds.

Reserves Payton Pritchard and Derrick White led a key surge late in the third and early in the fourth as the Celtics rallied.

“The first team was a little sluggish. We tried. We was giving it everything we got and just couldn’t find it,” Smart said. “And then those two came in and gave us the jump we needed. The energy definitely shifted with those two guys coming into the game.”

Pritchard scored 10, and White finished with 16 points — 11 in the second half — five assists and four steals.

Shai Gilgeous-Alexander led the Thunder with 37 points. Lu Dort scored 21, and Aleksej Pokusevski finished with 16 points and 14 rebounds.

All five starters scored in double figures for Oklahoma City, which couldn’t hang on after a solid start.

“There were a lot of bright spots. We really put it to them. We controlled the game on the road against a great team, which is a credit to our guys,” coach Mark Daigneault said.

The Thunder had just six turnovers in the first half, but seven in each of the final two quarters while falling to 2-5 on the road.

Boston coach Joe Mazzulla said the Celtics overcame the Thunder with defense and credited the scrappy play of Pritchard and White.

“I thought especially in the second half, we didn’t allow our lack of shot-making to affect our defensive effort,” Mazzulla said. “That to me is a sign of growth for the team.”

Pritchard hit a 31-foot 3-pointer with the shot clock about to expire late in the third, pulling Boston within nine. Pritchard then had a steal and a layup just before the buzzer, cutting the margin to 96-89 entering the final quarter.

Pritchard hit another 3-pointer in the opening minute of the fourth and Oklahoma City’s 15-point lead was down to 99-94 with 11:11 left.

Smart drew an offensive foul on Gilgeous-Alexander and a two-handed dunk by Tatum tied it at 107 as fans roared in approval of Boston’s surging momentum.

A three-point play by Dort tied it at 115 with 2:41 left, but Smart hit a 3-pointer to put Boston back up and White followed with another 3 after a miss by the Thunder at the other end.

STILL SCORING

The Thunder had scored 130-plus points in three straight games, including a 145-135 win over the Knicks in New York on Sunday. Coming just short at Boston with 122 points reminded the Thunder of their potential, Gilgeous-Alexander said.

“When we play to our identity, we can play with anybody,” he said. “We knew that going in — that we’d give ourselves a chance to win if we played our style and way and I think we did so for a majority of the game.”

TIP-INS

Thunder: Outrebounded Boston 51-46. … Oklahoma City was playing the second of a four-game trip with stops still to go in Washington and Memphis.

Celtics: G Malcolm Brogdon missed his third straight game with a tight right hamstring. … F Grant Williams received a technical foul with 7:31 left in the first quarter after complaining about a no-call when he went up for an offensive rebound. … Tatum received a technical 1:04 into the second quarter after a foul, although he appeared to be yelling at himself. … Boston Bruins winger David Pastrnak received a round of applause when he was shown sitting courtside during a stoppage in the second quarter.

UP NEXT

Thunder: Visit the Washington Wizards on Wednesday night.

Celtics: Visit the Atlanta Hawks on Wednesday night.