OKLAHOMA CITY -- It was easy to forget about Kyrie Irving in the first half of the Boston Celtics' 101-94 win over the Oklahoma City Thunder on Friday night.

The Celtics guard had only three points on a single field goal and went without an assist in the first two quarters.

But he erupted in the second half to finish with 25 points and help his team rally from a double-digit deficit for a seventh straight win.

"It feels good, understanding what we were battling, the type of first half we put out there," Irving said. "Man, it was ugly. It was an ugly first half. It wasn't pretty. We understand that. We don't want to get in the habit of that, getting down 18."

With just about four minutes left in the game, Irving launched a 3-pointer and was fouled by Thunder guard Russell Westbrook.

The shot dropped through the net, and though Irving missed the ensuing foul shot, he collected his rebound and put it up for another two points. That gave the Celtics a six-point lead.

"I knew Russ had five fouls," Irving said. "So just trying to attack him on that layup kind of gave us the separation we needed to feel comfortable."

Later, with less than 10 seconds to play, Irving hit a layup to seal the win.

Irving scored 15 points in the fourth quarter. Forward Al Horford also made big contributions with a couple of late 3-pointers to finish with 20 points.

"It looks good every time it leaves his hands, and it looks good in practice every time it leaves his hands," Celtics coach Brad Stevens said of Horford. "He's made himself into one heck of a shooter. He stayed ahead of the curve with where the game was going, and all the credit goes to him for that."

Paul George led the Thunder with 25 points, and Westbrook had 19 points, six rebounds and 11 assists.

Oklahoma City played perhaps its best defensive half of the season to open the game, holding Boston (7-2) to 37 points and a 31 percent shooting.

"Who we can be was right in front of us for the first 24 minutes," Thunder coach Billy Donovan said.

With time about to expire at the end of the second quarter, Irving desperately tried to chip away at his team's deficit.

But as he tried to maneuver around Thunder guard Andre Roberson and hook the shot over his head, Roberson stretched out his arm and swatted the ball down at the buzzer.

But the Oklahoma City defense faltered in the third quarter.

The Thunder led by as many as 18 in the first half, but the Celtics opened the second half with an 11-3 run as the Thunder went 3 of 10 from the field in the same span.

Boston outscored Oklahoma City 30-16 in the third and 34-23 in the fourth.

"We were playing a little slow," Westbrook said of the second half. "We came out a little lackadaisical and they capitalized on that."

When Westbrook picked up his fourth foul in the third quarter, he wasn't able to guard Irving as effectively.

"Obviously, you want to stay in the game, you've just got to figure out how to do it," Westbrook said of the foul trouble. "It takes you off your matchups and you've got to do different things."

The Thunder (4-4) had opportunities to pull away in the second quarter but couldn't stop Boston's Jayson Tatum. The rookie added seven of his 13 points in the second quarter.

Oklahoma City's offense hummed along in the first quarter, with the Thunder shooting 52 percent from the floor and 50 percent from beyond the arc.

But when the Thunder's defense cooled in the second half, its offense slowed down with it.

Oklahoma City finished shooting 40 percent from the field and 37.1 percent from 3-point range.

NOTES: Thunder G Russell Westbrook was called for a Flagrant-1 foul after hitting Celtics G Jaylen Brown in the face during a jump ball in the first half. ... Celtics F Marcus Morris made his season debut in the first quarter after missing the first eight games. He missed the start of training camp while on trial for aggravated assault in Arizona, and after being acquitted, Morris was held out of early regular-season games to get in back in playing shape. ... Celtics F Al Horford gave Billy Donovan a big hug before tipoff. Donovan coached Horford at Florida. ... Thunder C Steven Adams got into the holiday spirit early, wearing a 'Rick and Morty' cartoon Christmas sweater to the arena before the game. ... Both teams return to action on Sunday when the Celtics travel to Orlando and the Thunder head to Portland.