There is no official word as to what type of injury Campbell is nursing. There are two early candidates.
Greg Papa said that Campbell suffered a dislocated right shoulder, which might have taken him out for some period of time. Dislocated shoulders take some time to heal, but they usually take weeks rather than months. But it could also be a more serious collarbone injury (which the Raiders are running tests on), particularly a broken collarbone. That type of injury could knock him out for the majority of the season. In any case, we probably won't be seeing him the rest of the afternoon.