The 49ers signed one of their own free agents, offensive tackle Garry Gilliam, to a two-year contract on Tuesday.
Gilliam served as the team's backup tackle last season, a role he'll likely have again in 2018. Joe Staley is expected to start on the left side while Trent Brown plays on the right.
Brown, however, is not signed beyond the upcoming season and had surgery to repair a torn labrum (shoulder) in December. Gilliam, 27, likely will fill in during spring practices while Brown recovers.
Including the playoffs, Gilliam had started 34 games for the Seattle Seahawks before the 49ers picked him up last offseason. He started one game in 2017 before suffering an MCL sprain that landed him on injured reserve.
He joins quarterback Jimmy Garoppolo, defensive end Cassius Marsh and center Daniel Gilgore as free agents the 49ers have extended before the beginning of the free-agency period on March 14. Other players, such as running back Carlos Hyde and safety Eric Reid, are expected to test the free-agent market.