HOUSTON - James Harden tallied 37 points and nine assists to lift the Rockets to a 118-87 win over the Thunder on Sunday night.

Houston now holds a 1-0 series lead in the first round of the Western Conference Playoffs.

Russell Westbrook scored 22 points, 11 rebounds and seven assists, but didn’t have enough help from his teammates to pull off the upset on the road.

With Billy Donovan opting to switch on screens on defense, Harden was able to do anything he wanted on the offensive end of the floor. Whether it was Steven Adams, Taj Gibson, Jerami Grant or Enes Kanter, Harden absolutely exposed the Thunder’s defense and Donovan refused to adjust.

“Defensively I actually thought our first-shot defense was pretty good, now there were some things late where I thought we gave up too much at the rim, the deep paint was a problem for us,” Donovan said. “I think we did not make good enough decisions in terms of having enough resistance at the basket, some may have been them concerned about stopping the three, but I think we can do better in those areas than we did certainly tonight.”

Despite starting the game 0-for-4, Harden tallied 18 points by halftime to give the Rockets a five-point lead, then hit a 3-pointer on the first possession of the second half to set the tone for what was coming.

"I mean, obviously he scored a lot of points but I mean he took 28, 29 shots," Donovan said of Harden's performance. "I thought he was efficient with what he did but like I said, when you’re dealing with a team like them there’s a lot of pick your poison so to speak."

While Harden was the straw that stirred the drink, he wasn’t the only Rocket to play well. Just minutes after getting leveled by an epic Adams’ screen, Patrick Beverley drained two clutch 3-pointers to fuel a 9-0 run to put Houston up 73-62.

The Rockets led by 15 after three quarters, then opened the fourth on a 21-6 run to go up 30 points and put the game away.

Despite the Thunder leading the league in rebounding throughout the regular season, Houston dominated the boards to the tune of a 56-to-41 advantage while totaling 62 points in the paint.

Andre Roberson played solid on both ends of the floor and finished with 18 points and seven rebounds, but Westbrook and Grant were the only other Thunder players to score in double figures. Victor Oladipo struggled all night, going 1-for-12 from the field to total six points while Adams wasn’t much of a factor with his six points and five rebounds.

Beverley finished with a playoff career-high 21 points to go with 10 rebounds, while Nene notched 15 points off the bench with little resistance at the rim due to OKC’s suspect defensive game plan. Clint Capela was also solid with 14 points and seven boards and Lou Williams added 11 points.

The Thunder and Rockets will square off again in game two on Wednesday night.