Brandon Jacobs will make his 49ers debut tonight against the Seattle Seahawks, after missing the first six weeks with a knee injury. Jacobs was signed in the offseason away from the New York Giants to act as a third-down and goal-line back, and he'll finally suit up for the first time in 2012 with a chance to do that. However, Mario Manningham will not be out there with him, as he is inactive with a shoulder injury. Manningham has played in all six games and has 24 catches for 258 yards and a touchdown.
Additionally, offensive tackle Joe Staley is active just days after suffering a head injury in Week 6 against the Giants.
Fantasy Take: It will be interesting to see how Jacobs' role takes away from Frank Gore and Kendall Hunter in fantasy, as the 49ers are the number one rushing offense in the NFL so far this season. Gore has four touchdowns on the year and Hunter has 5.5 yards per carry in relief duty, getting about half as many carries as Gore.
It would be hard to imagine that Jacobs himself is going to have a role worthy of a fantasy roster spot, but he could have major implications on the running game as a whole and decrease the value of Gore a bit in fantasy. It's hard to not recommend starting Gore every week, but the Seahawks are ranked second in the NFL against the run and second in yards per carry allowed. This should be a very low-scoring game and even with Staley active, both offenses could struggle to score points.