Powell underwent an initial examination Saturday night, suffering the injury in the second quarter.
He was off to a blazing start in the game, scoring 16 points on 6-of-8 shooting in just more than 12 minutes.
Powell, 23, is 6-foot-3 and was acquired by the Blazers in a trade with the Raptors in February. Portland re-signed Powell to a five-year, $90 million contract in free agency.
The Blazers next play at the Clippers (0-2) on Monday at 10:30 p.m. EST.