HOUSTON – James Harden's first 3-pointer was an air ball. His next one missed badly, too. By halftime he'd missed four more from beyond the arc. But part of the reason Harden has turned himself into one of the leading candidates for MVP playing in Mike D'Antoni's pace-and-space system this season is that he has learned to do so many other things so well.

"Just being basketball-savvy, you know?" Harden said after the Houston Rockets' 118-87 win over the Oklahoma City Thunder on Sunday evening in Game 1 of their Western Conference first-round playoff series.

James Harden went for 37 points while Russell Westbrook had 22, along with 9 turnovers. AP Photo/David J. Phillip

"As a point guard I have to try to find ways to split the defense. They're switching with the big [man] and taking our 3-pointers away, so I just tried to get to the basket."

There are few players in the NBA who can drive into the teeth of the defense and score at the rim or find an open shooter out of that action like Harden. The Rockets' offense has been fueled by Harden's brilliance at that particular skill all season long.

Sunday night Harden was especially lethal, scoring 18 of his game-high 37 points in the paint on 9-of-13 shooting inside, to offset a woeful 3-for-11 effort beyond the arc. With Harden driving and kicking, the Rockets outscored the Thunder in the paint 62-38 to go with a 31-4 advantage in second-chance points.

"The turning point was not an exact moment, but offensive rebounds and second-chance points was what really killed us," Thunder center Steven Adams said. "The bigs, especially me, played trash on the reads, and the pick-and-rolls were absolute garbage. We have to get back to the drawing board."

The Thunder had hoped contesting Houston's 3-point shooters would slow down its historically good offense. But it ended up leaving gaping holes in the middle of the paint as bigs like Adams, Enes Kanter and Taj Gibson found themselves switching out onto guards on the perimeter and unable to recover in time to either contest the shot or be in good rebounding position.

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Oklahoma City led the NBA in rebounding this season. Sunday, they were outrebounded 56-41.

"They just did a great job getting offensive rebounds," Thunder guard Victor Oladipo said. "We have to do a better job as guards to rebound collectively as a team. It's not just on the bigs, it's on everybody to rebound."

Defending the Rockets' lethal outside shooting always requires a choice like that. Houston set single-season league records for 3-pointers made and attempted in 2016-17. Some teams choose to stay home in the paint and hope for a poor shooting night. Others, like the Thunder, choose to contest those 3s and dare Harden, Patrick Beverley or Lou Williams to beat them off the dribble.

Sunday night, Harden clearly won that game. He punished Oklahoma City's bigs every time they switched out onto him on the perimeter. He was 3-for-3 with Kanter defending him, with all three of those shots coming at the rim. Or, if Kanter didn't fully commit to the switch on the perimeter, and found himself in no-man's land in between, Harden found a teammate rolling to the basket for one of his game-high nine assists.

Kanter played only 16 minutes Sunday and scored eight points as the Rockets repeatedly seemed to target him in the pick-and-roll whenever he was on defense. Thunder coach Billy Donovan abruptly subbed out Kanter after a play in the fourth quarter, when Beverley exploited misplayed pick-and-roll coverage and found Clint Capela rolling to to the rim for a dunk.

"If they stay on the shooters, then we'll take layups," D'Antoni said, in one of his so-simple-you-wonder-why-anyone-thinks-basketball-is-complicated kind of statements. "If they rotate, then we'll take 3s. If you read the game right, you have to pick one or the other."

Harden has been reading the game right all season. It's why he's one of the co-favorites for MVP along with Thunder guard Russell Westbrook. Game 1 of this duel between the two former teammates went decidedly to Harden.

The Thunder point guard kept his team in it for the first half but played only 13 minutes in the second half as Houston was turning the game into a blowout. Westbrook finished with 22 points on 6-for-23 shooting, 11 rebounds, 7 assists and 9 turnovers in just over 34 minutes, with an uncharacteristically poor plus-minus rating (minus-25).

"We got to play and do a better job, starting with myself," Westbrook said. "I got to do a better job of taking care of the basketball and making some shots."

The Thunder got almost no offense from anyone beyond Westbrook and Andre Roberson (18 points). Fellow starters Adams (six points, five rebounds), Gibson (five points, one rebound) and Oladipo (six points on 1-for-12 shooting) offered little support.

Beverley defended Westbrook for most of the night, and also poured in 21 points, hit four 3-pointers and grabbed 10 rebounds in just under 26 minutes, despite being leveled by a sharp pick by Adams in the second half. That pick brought D'Antoni out of his seat, yelling at the referees, who didn't call a foul.

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Beverley got up, shook off the hit and kept playing. When he was subbed out a few minutes later, Houston Texans defensive lineman J.J. Watt -- sitting courtside -- was waiting with an admiring handshake.

After the game, Beverley said he thought it was a clean pick and had no issue with Adams.

Game 2 of the seven-game series is Wednesday in Houston.