The Pittsburgh Steelers have downgraded veteran defensive end Brett Keisel to "questionable" with a calf injury.

Keisel has missed four games with the injury, but practiced throughout the week and appeared on target to start on Sunday against the Buffalo Bills.

If Keisel can't go, Nick Eason and Ziggy Hood will be the team's starting defensive ends.

Pittsburgh Steelers at Buffalo Bills

Pittsburgh

Out: WR Antonio Brown (knee), DE Aaron Smith (triceps)
Doubtful: TE Matt Spaeth (concussion)
Questionable: DE Brett Keisel (calf), S Troy Polamalu (ankle)

Buffalo

Out: LB Keith Ellison (knee), DE Spencer Johnson (hamstring), LB Shawne Merriman (calf, achilles), G Eric Wood (ankle)
Questionable: CB Terrence McGee (knee), TE Shawn Nelson (illness), RB C.J. Spiller (hamstring)
Probable: T Demetrius Bell (knee), LB Chris Kelsay (knee), DT Kyle Williams (ankle)