Rockets coach Kevin McHale said after Houston's 92-73 victory that his star guard bumped knees with Memphis' Quincy Pondexter in the first quarter. Harden did not return after the injury.
"He iced it, and stuff, and we'll see how he feels (Saturday)," McHale said indicating that he didn't think the injury was serious.
Harden, who entered the game as the team's leading scorer in the preseason with a 20.8 average, connected on a 3-pointer from the right wing with 4:35 left in the first quarter and went down to the court in front of the Rockets bench when he was fouled by Pondexter.
Harden eventually got up, made the ensuing free throw and went straight to the locker room at the next stoppage of play.
Harden finished with six points and four rebounds in his 7-plus minutes before the injury.
Marc Gasol led Memphis with 17 points, but connected on only 4 of 13 shots.
The game was a bit chippy at times with Gasol and the Rockets Dwight Howard earning double technicals in the first half, and Memphis forward Ed Davis drawing an ejection with a flagrant foul in the fourth.
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MEMPHIS, TN - OCTOBER 25: Quincy Pondexter #20 of the Memphis Grizzlies drives to the basket against James Harden...
These two teams begin the regular season on Wednesday, Oct. 30. Houston faces Charlotte at home and brings a 5-game winning streak against the Bobcats into that matchup. Memphis opens up at San Antonio in a rematch of last year's Western Conference finals, a 4-0 sweep for the Spurs.