Portland placed Williams in concussion protocol Tuesday, and he's been ruled out for Wednesday's game against the Pacers.
With Deandre Ayton (finger) and Donovan Clingan (knee) sidelined, Williams made his first start of the season Monday in Memphis but lasted only 12 minutes before suffering the concussion. The oft-injured big man will have a few hurdles to clear before suiting up again, but he can be considered questionable for Friday's game against the Kings.