Pryor initially picked up the problem during his side's loss to the Philadelphia Eagles last weekend, but he was still able to play in yesterday's 24-20 defeat to the New York Giants, wearing a knee brace throughout the match.
The 24-year-old picked up a touchdown early in the first quarter but rushed for a career-low 19 yards during the match and afterwards admitted that he did not feel like himself due to the injury.
"My knee is banged up. I've got a sprained MCL. It just got worse during the week. So I was just trying to come out and play and try to help the team but just didn't feel well today," Pryor told reporters.
"I couldn't get any push-off on my leg. I couldn't explode in the passing game, couldn't explode in the running game."
The only other quarterback on the Raider's active roster is undrafted rookie Matt McGloin, although they do have Tyler Wilson on the practice squad.