The 6-foot-4, 230-pound Savage first joined San Francisco on Oct. 16 before being waived on Oct. 20. Savage returned on Oct. 22, but was waived Thursday leading to Friday’s re-signing.
Savage, who spent the offseason with the New Orleans Saints, provides depth at the quarterback position with Nick Mullens and C.J. Beathard, who did not play Thursday night while nursing a wrist injury.
The Niners haven’t announced who will start in Week 10, but Mullens made a strong case for the job after a three-touchdown performance in a 34-3 win over the Raiders.
Meanwhile, Mostert led the Niners in rushing Thursday night with 86 yards and a touchdown on seven carries before suffering a gruesome broken forearm in the third quarter. His agent announced Mostert underwent surgery Friday.