The 22-year-old Spurs star took a knee to the floor on impact to the knee and also absorbed contact to the face, prompting an extended stoppage as medical staff tended to him.
Wembanyama stayed on the floor for a moment while teammates huddled around him, then got up, spoke to other Spurs players, and headed straight to the locker room.
San Antonio trailed the Blazers in the second quarter at the time, adding concern for the team as it sought to hold off Portland without its cornerstone rookie.
The Spurs have noted that Wembanyama previously dealt with a rib injury late in the regular season; more information on his condition and availability will be provided as it becomes available.