Victor Wembanyama missed the San Antonio Spurs' 140-113 loss to the Sacramento Kings on Friday due to low back soreness.
Wembanyama is considered day-to-day with the injury.
Wembanyama appeared to have suffered the injury on Tuesday night against the Suns when he was whistled for a charge against Bradley Beal.
"I don't think [the injury] was on a certain play. I'm sure that play didn't help. But I don't think it was one particular play," said Mitch Johnson.
Johnson is hopeful that Wembanyama could return on Sunday.