DALLAS -- Rookie of the Year candidate Victor Wembanyama was a late scratch for Saturday night's game against the Dallas Mavericks after spraining his right ankle when he stepped on a ball boy during his pregame warmup, according to a San Antonio Spurs spokesman.

The ball boy was standing on the baseline when Wembanyama stepped on his foot after making a driving layup over a Spurs assistant coach, causing the 7-foot-4 rookie's right ankle to roll.

Wembanyama had the ankle retaped, but the Spurs decided to sit him out after further evaluation.

"If it was a playoff game, I probably would've played him," Spurs coach Gregg Popovich said after the 144-119 loss. "He's not happy about it, but I would rather err on the conservative side since it's the same ankle that you just got a time limitation on. But just a freak, freak accident before the game."

Wembanyama sat out Tuesday's loss to the Milwaukee Bucks because of soreness in his right ankle. He played 22 minutes in Thursday's loss to the Chicago Bulls, and Popovich said during his pregame availability that the plan was for Wembanyama to be on a minutes restriction again.

Popovich, who is in his 28th season as San Antonio's head coach, said he had never seen a player injured in similar circumstances.

"You see it on the film, and you can't believe it," Popovich said.

Wembanyama, the No. 1 overall pick, is averaging 18.5 points, 10.7 rebounds and 3.0 blocks. He has played in all but three games this season.