HOUSTON -- When the opportunity presented itself for James Harden to seize the moment, Harden did precisely that. His nonchalance afterward was a reflection of his self-confidence when the Rockets need Harden the most.

Harden parlayed a torrid shooting stretch in the third quarter into his league-leading 49th double-double as the Houston Rockets topped the Memphis Grizzlies 123-108 on Saturday night at Toyota Center to gain a split of the season series.

Harden scored 20 of his game-high 33 points on 6-of-7 shooting from the field in the third quarter, including 15 consecutive points for the Rockets (44-19), who stretched a two-point lead to their first double-digit advantage at 72-62 on a Harden dunk with 6:06 left.

It wasn't until Harden caught fire that the Rockets gained separation, yet Harden didn't view his explosion as anything extraordinary.

"Score the basketball and be aggressive," Harden said matter-of-factly when asked what inspired his surge. "That's what I've been doing."

Harden added 11 assists and Rockets center Clint Capela paired a career-high 24 points with 11 rebounds to stamp his workmanlike performance.

Eric Gordon (18 points, 6 of 8 on 3-pointers) and Nene (11 points) paced a Houston bench that contributed 45 points. The Rockets also finished 18 of 42 on 3-pointers.

Four Memphis starters scored in double figures, led by guard Mike Conley (23 points, seven assists, six rebounds, two steals). Center Marc Gasol chipped in 17 points, seven assists and four blocks and forward JaMychal Green had 20 points and 10 boards as the Grizzlies (36-27) lost for the fifth time in eight games.

Houston claimed the final two games of the season series by an average of 19.5 points after blowing a 15-point third-quarter lead in a 110-105 home loss on Jan. 13. The Rockets and Grizzlies could square off in the first round of the postseason.

"They're very tough to defend when they're shooting the ball from the 3," Grizzlies guard Tony Allen said. "Harden is coming and he's forcing the ref to blow the whistle, and when you have that clicking in makes it tough."

Before Harden caught fire, the Grizzlies remained close, countering the Rockets' perimeter prowess with 60 points in the paint. But Memphis slipped into a deficit midway through the first and never reclaimed the lead despite that interior edge.

When the Grizzlies closed within 44-42 on a Gasol jumper with 6:49 left in the first half, Harden answered with four consecutive points.

When Memphis pulled to within 57-55 on a Green layup with 10:30 remaining in the third quarter, Harden delivered four free throws, a transition 3-pointer, and two additional treys before his transition dunk provided Houston the working margin its labored to build.

"He just has to read the game," Rockets coach Mike D’Antoni said of Harden. "He does it great. He got off in the third quarter. We had 38 points in that quarter and he was huge."

Once Harden helped build the advantage to double digits, Memphis got no closer than eight points the rest of the game. Houston stretched its lead to 109-89 on a Capela alley-oop dunk with 6:13 left. Harden, of course, had the assist.

"We stopped defending the 3-point line and it just doesn't take long with them," Grizzlies coach Dave Fizdale said. "It's just like three or four possessions can bust a game open. That's what happened.

"A couple coverages where we broke down and we didn't stay disciplined in what we were doing. And that guy James Harden is pretty good too."

NOTES: Rockets G James Harden produced his 20th 30-point, 10-assist game this season. Harden had 21 such games in his career before 2016-17. ... Grizzlies F Chandler Parsons started back-to-back games for the first time this season, finishing with two points and seven rebounds over 19 minutes. Parsons has been slow to return to form following multiple knee surgeries. He logged 23 minutes and posted seven points and four rebounds in Dallas on Friday night. ... Rockets G Eric Gordon set an NBA record for 3-pointers by a reserve, increasing his season total to 180 off the bench (202 overall). Bucks F Mirza Teletovic produced 179 3-pointers off the bench for the Phoenix Suns last season.