Darrius Heyward-Bey became the latest Raiders wide receiver to miss practice time because of injury, as he failed to complete the session Thursday with a knee issue.
"Obviously, we've got to get him in, check on him, see where we are," coach Hue Jackson said. "Hopefully, he'll be OK."
Jackson said he didn't know if Heyward-Bey would undergo extensive medical testing.
"All I know is he didn't finish," Jackson said.
The Raiders' other starting wide receiver, Jacoby Ford, missed practice for the second straight day with a hamstring issue, and his status remains unclear for Sunday's game in Buffalo.
Louis Murphy has been out since training camp after sports hernia surgery and is hoping to be ready for the home opener Sept. 25 against the New York Jets.
Heyward-Bey had little to say in the open locker room session other than, "We'll see."
The third-year wide receiver is coming off a solid opener in which he had four catches for 44 yards, including a 9-yard gain on a second-and-8 play during the game's final drive, when the Raiders killed the clock against Denver.
Should the Raiders be without both Ford and Heyward-Bey, rookie Denarius Moore, Chaz Schilens, Nick Miller and Derek Hagan would be counted upon to pick up the slack.
Moore was the only one of the four to have a pass thrown his direction the opener, and it was incomplete. Schilens played sparingly, and Miller returned punts. Hagan was inactive after leading the Raiders in receiving during the preseason.
Those with limited participation were tight end Kevin Boss (knee), Heyward-Bey and running back Darren McFadden (shoulder). McFadden looked fine during the media window of practice.
An NFL source said no decision was expected Thursday.
Pryor didn't attend the hearing. He was on the field practicing with his personal quarterback coach after the Raiders session.
"Some of those things are concentration errors, and when you have great pass rushers on the outside like we faced last week, sometimes the tackles get a little nervous and they try and get set a little quicker than they need to," offensive coordinator Al Saunders said. "We've worked real hard on that, establishing what they need to do on the edge to be more consistent."