Pryor first hurt the knee in the second half of a loss to Philadelphia on Nov. 3 and eventually left that game early. He said the knee got worse during the week of practice but he kept that information away from his coaches.
"I don't know that there was any type of disconnect or anything," coach Dennis Allen said. "We evaluated him during the week in practice and things seemed to be OK, but obviously, when you got in the game, it was pretty evident early in the game that he just didn't have that same explosiveness that he normally has."
Pryor only ran the ball five times for 19 yards and took four sacks as he struggled to get away from the Giants pass rushers on his bum knee.
The Raiders also could be without running back Darren McFadden this week. McFadden missed another practice as he recovers from a sore hamstring that forced him to miss last week's game.
Oakland did get some positive news on the injury front with right tackle Tony Pashos returning to practice for the first time since injuring his hip in the first half at Kansas City on Oct. 13 and left tackle Jared Veldheer practicing for the first time since tearing his left triceps in training camp.
The Raiders have three weeks to decide whether to activate Veldheer from the short-term injured reserve list or shut him down for the season.
Pryor's status is a more pressing concern.
After a promising start to the season, Pryor has struggled mightily in recent weeks, once again raising questions about whether he can be consistent enough to succeed as an NFL quarterback.
Since the start of Week 6, Pryor has completed 61 of 120 passes for 714 yards with one touchdown and eight interceptions. Pryor is last in the NFL in that span in completion percentage (50.8) and passer rating (44.2) and is tied for the most interceptions. Pryor has gone 112 straight passes since throwing a touchdown pass.
"I still think I bring excitement," he said. "I still make people, their eyes wide on plays. On some of the stuff that happens, when you watch a lot of young guys you tend to make some mistakes or you tend to give away something to the defense because they're watching film and maybe it's a concept they realize what it is. I'm not really too worried about a loss of confidence at all. It's just a learned lesson and try to put your head down and keep digging. Because you know it's going to be brighter as it goes on."
With Pryor sitting, undrafted rookie free agent Matt McGloin got his first extensive practice time with the first-team offense all season. McGloin, who entered camp out of Penn State as the fourth quarterback, moved past Matt Flynn and Tyler Wilson on the depth chart and now could get a chance to start this week.
McGloin played briefly in relief against the Eagles, completing 7 of 15 passes for 87 yards in his only action of his rookie season.