Running back Brandon Jacob's debut with the San Francisco 49ers will have to wait at least another week.
Jacobs is among those inactive for San Francisco against the Buffalo Bills on Sunday. The big, burly former New York Giants running back has not played since injuring his left knee in the preseason. He practiced this week without limitations and had declared himself healthy enough to play.
Rookies LaMichael James and A.J. Jenkins also were inactive for the 49ers.
The Bills got a boost with safety Jairus Byrd (hip) and wide receiver Ruvell Martin (ankle) on the active roster. Both were listed as questionable earlier in the week. Martin also plays on special teams.