The 49ers are already in the process of signing running back Christian McCaffrey, likely for a few more weeks. Now, at least temporarily, they are without his backup, Jordan Mason.

Mason was injured during a 14-yard run when he landed on his left shoulder as safety Julian Love’s weight landed on him. After the match he remained on the ground.

Mason went to the X-ray room and his return was questionable.

He came into the game with a league-leading 105 carries for 536 yards and three touchdowns and has rushed for 65 yards on eight carries tonight. Mason also has a 9-yard reception.

Rookie Isaac Guerendo has replaced Mason.

The 49ers lead the Seahawks 16-0.