Coach Chan Gailey said Monday it wasn't knee surgery, but it was related to McGee's recent knee soreness.
McGee missed Buffalo's 38-14 loss to the New York Jets Sunday, and will be out for the upcoming game against Jacksonville (2-2). The Bills have their bye following that game.
Tight end Shawn Nelson is eligible to be reinstated this week after serving his four-game NFL suspension for violating the league's substance abuse policy. However, the Bills may use a one-game exemption for him after Nelson revealed Monday that he underwent groin surgery four weeks ago.