The team named Jacobs among its inactive players against Buffalo on Sunday.
Jacobs isn't really needed at this point. So, even though he's healthy enough to practice following a knee injury suffered in August, the veteran running back will sit out this game. His former team, the New York Giants, visits Candlestick Park in one week.
Receiver A.J. Jenkins and running back LaMichael James are also inactive. The 49ers haven't needed their rookie draft choices to this point. Having Ted Ginn Jr.Jr. healthy at receiver allows the 49ers to keep active five veteran wideouts with starting experience, including two with considerable recent experience as returners (Kyle Williams, Ginn).
Also inactive for the 49ers: guard Joe Looney, nose tackle Ian Williams, safety Trenton Robinson and quarterback Scott Tolzien. Veteran nose tackle Isaac Sopoaga, sidelined by a knee injury recently, is active. He might not be needed much, however, because the Bills play primarily with three-plus wide receivers at a time. As a result, the 49ers' base defense might not play much.