BOSTON (AP) — Russell Westbrook scored 26 points, hitting a pair of 3-pointers in the final 91 seconds on Monday night to help the Oklahoma City Thunder pull away from Boston and beat the slumping Celtics 97-88.

Kevin Durant scored 28 with seven rebounds for the Thunder, who won their seventh consecutive game. Thabo Sefolosha scored 12 of his 19 points in the fourth quarter, and Kendrick Perkins had seven points and five rebounds in his first game back in Boston since the trade that sent him to Oklahoma City and broke up the starting lineup from the Celtics’ 2008 NBA championship team.

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Oklahoma City Thunder center Kendrick Perkins, a former Boston Celtic, embraces Boston Celtics coach Doc Rivers before a game Monday in Boston. AP

Paul Pierce scored 24 points, Kevin Garnett had 12 points and 12 rebounds and Jermaine O’Neal had 12 points and 11 boards for the Celtics. Rajon Rondo scored 12 points with nine rebounds and nine assists for Boston, which lost its fifth straight game for the first time in the New Big 3 era.

Perkins went over to the Celtics bench before the opening tip to hug the coaches and chest-bump some of his former teammates, and midway through the first quarter a video tribute was played on the scoreboard. The crowd gave him a standing ovation, which Perkins acknowledged by walking to center court alone and waving.

Durant had a tomahawk slam to give the Thunder an 83-78 lead, but Boston cut the deficit to 83-80 with 2:25 to play. Westbrook cut across the lane and whipped a two-handed pass to Sefolosha in the corner for the 3. After Rondo scored on a putback, Westbrook hit a 3-pointer of his own — then celebrated by strutting down the sideline.

After Garnett hit Mickael Pietrus to set up a Celtics 3-pointer, Westbrook answered again to make it 92-85. The Thunder went just 2 of 11 from 3-point range in the first three quarters, but 5 of 8 in the fourth.

The Celtics had not had a five-game losing streak since they lost seven straight and eight of the last nine games of the 2006-07 season, a year when they also had an 18-game losing streak that was the longest in franchise history. That summer they began assembling the New Big 3, bringing in Garnett and Ray Allen to join Pierce — and Rondo and Perkins.

Perkins was the starting center on the team that won the championship in 2008. But when the Celtics returned to the finals in 2010, Perkins injured his knee in Game 6 against the Lakers and missed Game 7, which Los Angeles won 83-79.

With Perkins’ rehabilitation due to last well into the following season, general manager Danny Ainge signed Shaquille O’Neal and Jermaine O’Neal. Confident that they would remain healthy contributors, Ainge traded Perkins to Oklahoma City for Nenad Krstic and Jeff Green, but neither of them was able to remain in the lineup and the Celtics lost in the second round of the playoffs to Miami.

The trade looked even worse when Green was diagnosed with an aortic aneurysm, requiring surgery that put him out for this entire season. He is now a free agent.

The Thunder led most of the first half, including a 10-point lead early in the second quarter and a 46-39 advantage at the half. Pierce, who scored Boston’s last six points in the second quarter, scored three more quick baskets early in the third, and back-to-back-layups by Jermaine O’Neal left it tied 57-all with 5 minutes left in the third.

It was 65-62 when Oklahoma City scored the last seven points of the quarter to make it a 10-point game.

Notes: New England Patriots cornerback Devin McCourty and receiver Julian Edelman took time off from their preparations for the AFC championship to attend the game. … The teams split their games last year, each winning on the road. Durant missed the game in Boston with a sore left ankle. … Thunder guard Reggie Jackson played at Boston College.