The 49ers placed George Odum on injured reserve Monday.
Odum tore his biceps against the Seahawks in Week 12.
He appeared in 11 games this season with a team-high 10 special teams tackles.
The 49ers activated defensive lineman Robert Beal Jr. off injured reserve in a corresponding move.
Beal, a fifth-round rookie, went on the injured reserve list Aug. 30 with a hamstring injury. He was one of three players the 49ers designated to return to practice Nov. 6.
