49ers running back Brandon Jacobs hasn't played since sustaining a knee injury during an Aug. 18 preseason game. He is listed as questionable to play Sunday versus the Bills, but he participated fully in each practice this week and is expected to make his regular-season debut.
This isn't about Jacobs' fantasy prospects against an awful Bills run defense. This has more to do about the possible impact on Frank Gore. First of all, it's another guy in San Francisco's backfield who is going to take away a few carries from Gore. But oh, the value of those carries. Two of Gore's three touchdowns this year have come from no more than 2 yards out. If Jacobs had been available earlier, it's very plausible that Gore wouldn't have been on the field to take those payoff carries.
Simply, Jacobs' presence will most likely mean a significant drop in Gore's touchdown chances. This week, because it's the Bills, Gore is still a quality RB2 even if Jacobs is active.