"He's taken a step back," Gailey said Wednesday via CBSSports.com. "He's going to struggle to make some practice this week, so we'll have to see. It may be a game-time decision on him."
If Byrd can't recover in time to participate on Sunday, George Wilson will slide over and play free safety, and Da'Norris Searcy will get a start at strong safety.
Meanwhile, three other players missed practice on Wednesday, per BuffaloBills.com: running back Fred Jackson, wide receiver Ruvell Martin and defensive tackle Marcell Dareus. Jackson remains shelved with a knee injury, while Dareus is back in Alabama attending the funeral of his slain younger brother. Martin has an ankle injury. Dareus is expected to play on Sunday, while Jackson will sit; for now, the jury remains out on Martin and, far more importantly, Byrd.