49ers lose Staley to knee contusion

SAN FRANCISCO -- Joe Staley's return is doubtful after the 49ers' starting left tackle suffered a knee contusion.

The 49ers did not say whether this was the same knee Staley injured earlier in the season. I did notice Staley struggling to hold his ground on one play when his man batted a pass at the line of scrimmage.

Barry Sims is playing left tackle.

Also on the injury front, Frank Gore started the second half for the 49ers after missing the final six snaps of the second quarter.