Marcus Smart stars as Celtics beat Thunder in Oklahoma City

Taking on the challenge of going toe-to-toe with Russell Westbrook, Smart shot 9-for-14 from the field and hauled in eight rebounds as the intense guards battled for four quarters.

"That's the type of guy that Russ is," Smart told reporters. "He loves challenges. He is going to try to do his best every time. And vice versa with me. You put two guys like that going against each other, obviously you're going to knock heads."

Boston guard Avery Bradley contributed well off the bench as the visiting reserves torched Oklahoma City in the fourth quarter, the Celtics (5-4) building an 11-point advantage and controlling the game midway through the period.

Oklahoma City brought its starters back in but they lacked the energy to contend with the scrappy Boston squad. They were beaten to loose balls and rebounds and were just out-hustled as the Thunder never got closer than 12 points the rest of the way.

Westbrook had a game-high 27 points on 5-of-20 shooting. He shot 2-for-10 from behind the three-point arc but was 15-for-17 from the free-throw line.

Forward Serge Ibaka was the only other Thunder player to score in double figures, finishing with 16 points and 10 rebounds. Center Enes Kanter was held to eight points and two rebounds.

"I got no answers for that," Kanter said of his team's offensive performance as the Thunder dropped to 6-4 overall, 1-1 without injured forward Kevin Durant.

Boston guard Isaiah Thomas scored 20 points to go along with eight assists. Center Jared Sullinger owned the glass, as he pulled down 15 boards. As a team, the Celtics out-rebounded the Thunder 47-34.

"We need to pick our intensity up physically," Westbrook added. "Just wasn't ready."

Close to where he played his college ball, Smart started the night as if he were still representing Oklahoma State. He shot 4-for-6 in the first quarter to knock in nine quick points.

"I think that he likes this gym," Boston coach Brad Stevens said. "This is the gym he always shoots it well in, right? I think his offense has really improved."

While Smart was attacking the basket, Westbrook was doing his damage from the perimeter. He attempted five three-pointers in the first eight minutes of the game. He entered the game averaging only five three-pointers a game on the season.

Oklahoma City was able to build a 10-point lead with less than a minute left in the first half but the Celtics cut the deficit down to 52-45 by halftime.

The Celtics stormed all the way back in the third quarter to tie the game at 72-72 as the visitors fed off a game-changing shift in momentum.