The Timberwolves trailed the Rockets 68-79 at that juncture of the game, and are fighting to leave Houston with a win, albeit without their best player.
Midway through the third quarter, leading scorer Jimmy Butler snatched a rebound and pump faked over Rockets defenders before sinking to the floor, clutching his right knee.
Teammates, coaches and athletic trainers tended to Butler, who had to be helped off the court.
The injury itself doesn't look good, as Butler was not able to put any weight on the knee in question.
Butler was seen hopping on one foot in the Toyota Center hallway as he headed to get an X-ray. The mood in the Wolves' locker room was also said to be "somber".
Prior to the incident, Butler scrambled for a rebound which ended in Nene tumbling backward onto his leg.
Butler told ESPN's Cassidy Hubbarth prior to Friday's game that he'd rather sit out the National Basketball Association showcase than miss time with Minnesota.
A video showed Butler appearing to say "It's torn".