Boston relentlessly hunted for the slow-footed Danilo Gallinari on defensive switches in the second half, and Walker, who had been relatively quiet to this point, used that matchup to drill back-to-back 3-pointers late in the fourth to stretch the lead to 109-101.

Jayson Tatum had 26 points and 11 rebounds and Kemba Walker added 27 points for the Celtics, who made 16 of 36 3-pointers as a team.

OKLAHOMA CITY— The Celtics welcomed back some reinforcements and muscled their way to a 112-111 win over the Thunder on Sunday afternoon, their seventh in a row.

The Thunder made one final push, pulling within 110-106 on a Dennis Schroder 3-pointer with 46.2 seconds left. Walker made one of two free throws before Chris Paul raced the other way for a layup that made it 111-108 with 16.4 seconds left.


After a timeout, Gordon Hayward tried to beat the Thunder’s attempts to foul him by driving to the hoop for a dunk, but his attempt was blocked, and the Thunder raced upcourt with a chance to tie. Then Marcus Smart made the defensive play of the game, swiping the ball away from Shai Gilgeous-Alexander.

Observations from the game:

■ Tatum had just 7 points in the first half, but he started to look like the All-Star that he is in the second. In one third-quarter stretch he completed a pair of tough drives for layups before drilling a 3-pointer that put the Celtics ahead 70-68 after trailing 62-52. Then near the start of the fourth he left three defenders in his wake on a swerving drive to the basket before adding a fast-break slam.

■ It was enjoyable to watch the 6-foot-8-inch Tatum and the 6-foot Paul battle while defending each other. It seems like there should be mismatches both ways, but the two really went after each other.


■ In a rare occurrence, the Celtics actually had their entire regular starting lineup, as Daniel Theis and Jaylen Brown returned from their respective ankle sprains. With all of the offensive weapons out there with him, center Daniel Theis was an important safety valve down low for the Celtics. The big man had 13 points, 11 rebounds and 5 assists.

Daniel Theis tries to steal a rebound from Oklahoma City’s Steven Adams in the second half of Sunday’s game. Kyle Phillips/FR171277 AP via AP

■ Walker ended up switched onto the 6-foot-10, 225-pound Gallinari a few times in the first half, and it usually did not end well. In the first quarter he committed a shooting foul before Gallinari drove past him for a dunk. After that play, Hayward pulled Walker aside and appeared to say something about how they would handle that mismatch.

■ Enes Kanter received a loud ovation when he checked in midway through the first quarter. Kanter was a crowd favorite here when he played for the Thunder from 2014-17, and he recently announced plans to open up a charter school in the city.

■ The Thunder used a pair of big runs to take a 61-52 lead to halftime. They closed the opening quarter with a 10-0 flurry before adding a 15-2 burst in the second. That surge came with Marcus Smart on the bench after collecting his third foul. Celtics coach Brad Stevens generally does not react to first-half foul trouble, but his trust in Romeo Langford combined with having all of his top weapons available might have made him comfortable taking the safer route here.

■ Langford had two good games in Boston this week, and those performances probably helped him get on the floor in the first half. But he had a bit of a rookie education on defense, twice biting on pump fakes before committing fouls. His third foul did not appear to be his fault, though, as he absorbed a forearm from Gallinari but did not get the call over the veteran.


Jaylen Brown waits to lower the boom on Oklahoma City’s Dennis Schroder n the first half of Sunday’s game. Kyle Phillips/FR171277 AP via AP

■ Brown, who returned after missing a game with his nagging ankle injury, appeared to tweak the injury midway through the third quarter. He yelled out in frustration as he sat on the ground before getting up and limping directly to the bench. But he was back on the court just a couple minute later, and he appeared to take out his frustration about the ankle on the Thunder. In quick succession he scored inside, drew a foul on a hard drive, and then swished a 3-pointer.

■ Smart and Dennis Schroder had a third-quarter collision that was meant for Hollywood. Schroder tried to sell a charge on Smart’s drive. He was whistled for a blocking foul, but Smart probably didn’t know that yet. Then when Hamidou Diallo made contact with Smart’s face, Smart flung backward and completed some sort of flying kick through the air before taking a hard fall. In other words, it was all very Marcus Smart.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.