BOSTON -- Two of the best guards in the NBA put on a show Friday night at TD Garden.

Russell Westbrook wound up the winner in what amounted to a personal showdown with Isaiah Thomas.

Westbrook, adjusting quite well to life without Kevin Durant, registered his 14th triple-double of the season and saved his best for last.

He scored 12 of his 45 points in the final 1:36, including back-to-back 3-pointers, and had his team's last 15 points to lead the Oklahoma City Thunder to a 117-112 victory over Boston, ending the Celtics' four-game winning streak.

"Isaiah was playing well, but I don't need fuel from nobody, from any other player, to get me going," said Westbrook, who also had 11 assists and 11 rebounds in his third straight 40-point game -- all in 34:50 of playing time.

As far as his fourth-quarter mindset, Westbrook said, "Why not. Why not. That's my motto. That's what I stand by. That's what I believe in."

Thomas had 34 points and 10 assists in 34:17. Afterward, he was frustrated over his team dropping to 6-6 at home (11-7 on the road) but said his team "can't hang out heads" over this loss.

As far as the guard duel, Thomas said, "I take every challenge personal. Every guard that steps in my way, it's always personal, and I'm a competitor."

Westbrook started slowly but scored 14 points in the second quarter to give him 16 at half. He then scored 29 of his team's 59 points in the second half and had 20 in the fourth quarter.

Thomas scored 18 in the fourth and is averaging 31 points per game in the last five.

Asked if Thomas' eruption opened his eyes, Westbrook said, "My eyes never close."

"Russell's a tough matchup for everybody, but I thought their length and athleticism was certainly a factor in a lot of ways," Celtics coach Brad Stevens. I thought we did a lot of good things. I thought they did more good things and they won the game."

Rookie Domantas Sabonis scored 17 of his career-high 20 points in the first half and Enes Kanter had 20 points and six rebounds off the bench for the Thunder (18-12).

Westbrook finished 13 of 25 from the floor, including 5 of 7 from 3-point range.

"They're scrappy, man," Westbrook said of the Celtics. "They're a team that competes on both sides of the ball. They’ve definitely gotten better from last year."

Thomas was 12 of 22 from the floor but just 2 of 8 from 3-point range. Al Horford had 23 points, Amir Johnson added 17 and Avery Bradley scored 17 for Boston (17-13).

OKC went 4:35 without a field goal in the fourth quarter, but a Jerami Grant dunk and an old-fashioned three-point play by Westbrook gave the Thunder the lead by a point with 2:50 left.

The Celtics fouled Andre Roberson on purpose on two straight possessions and he missed all four free throws. But Thomas turned the ball over, Westbrook grabbed it and raced down the floor, scoring as he was being fouled by Horford.

Westbrook, who came in averaging 31.3 points, 10.5 rebounds and 10.8 assists, missed the free throw and the Celtics had it back with 1:36 left. Thomas rimmed a trey and Westbrook calmly made one at the other end.

"I think he was really efficient. That's the thing we talk about ... being efficient, and he was really efficient (four turnovers)," Thunder coach Billy Donovan said of Westbrook. "He didn't take a lot of shots but the shots he took, he made. He took good ones."

After scoring 36 of his career-high 44 points in the second half at Memphis, Westbrook had 14 of his 28 in the fourth quarter at Indiana on Thursday night -- and he did it again at crunch time in this one.

"He's been really good all year in being able to do that," Stevens said.

NOTES: Thunder G Victor Oladipo missed his sixth straight game with a wrist injury. ... The Celtics, who opened a stretch of 16 of their next 22 games at home, are in New York to play the Knicks Sunday, while the Thunder host the Minnesota Timberwolves later that night. “You know, if there weren’t Christmas trees and lights and everybody talking about Christmas I wouldn’t even know what day it is,” said Celtics coach Brad Stevens.... G Isaiah Thomas came in with 121 points and 24 assists in the last four games, all wins, making him the first Celtics player since Larry Bird in 1990 to average 30 points and six assists in four straight wins. ... Thunder G Cameron Payne, out all season because of a broken foot, was back on the court with his teammates during Friday's shoot-around but still has a ways to go in his comeback. "It's good that he can get back on the floor and can kind of cut, move and shoot," coach Billy Donovan said.