The San Antonio Spurs have ruled out star Victor Wembanyama for Thursday’s game against the Chicago Bulls at Frost Bank Center because of bilateral lower back pain.

The 20-year-old Wembanyama appeared to be injured with 2:23 left in Tuesday’s 104-93 loss to Phoenix when he received an attack whistle after colliding with Bradley Beal. He remained in the game until he was substituted with 6 seconds left.

As Wembanyama left the pitch after the defeat he appeared unwell.

But interim coach Mitch Johnson said he was unsure about the extent of Wembanyama’s injury.

Wembanyama, San Antonio’s leading scorer, is averaging 23.5 points, 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 was forced to miss three games in November due to a bruised right knee.

It’s likely that the Spurs will use Zach Collins in Wembayama’s place, in addition to increasing the workload of reserve center Charles Bassey.

In other injury news: Backup point guard Tre Jones will miss his second game after suffering a sprained left shoulder in a win at Sacramento on Sunday.