The 49ers put veteran C Eric Heitmann on injured reserve on Tuesday, opening up a roster spot for rookie LB Thaddeus Gibson.
Heitmann, a ninth-year veteran, has not played this season after suffering a neck injury in training camp. He started all 16 games last season.
The Niners claimed Gibson off waivers from the Steelers on Monday.
The way we see it
San Francisco was hopeful that Heitmann would be able return, but they decided they needed to take his roster spot, which they used for Gibson. Sixth-year veteran David Baas has played well in Heitmann's spot this season.