The San Antonio Spurs were without star Victor Wembanyama for Thursday night's 139-124 home loss to the Chicago Bulls due to bilateral low back soreness.
Wembanyama, 20, appeared to have been injured with 2:23 remaining in Tuesday's 104-93 loss at Phoenix, on a play that saw him get a whistle for a charge after a collision with Bradley Beal. He remained in the game until subbing out with 6 seconds left.
Walking off the court after the loss, Wembanyama appeared to be in discomfort.
But interim coach Mitch Johnson said he was not certain of the extent of Wembanyama's injury.
San Antonio's leading scorer, Wembanyama is averaging 23.5 points with 10.4 rebounds, 3.8 assists and a league-high 3.4 blocks and was named the Western Conference Defensive Player of the Month on Tuesday.
Wembanyama sat out three games in November because of a bruised right knee.
Also Thursday, backup point guard Tre Jones missed his second game after sustaining a sprained left shoulder Sunday in a win at Sacramento.