With Christian McCaffrey out, Jordan Mason was a revelation. He is one of the best running backs in the NFL.

Can the San Francisco 49ers get similar production from their third running back on the depth chart? On Thursday evening they had to wonder.

Mason got off to a good start on Thursday night when he was tackled and immediately grabbed in the shoulder area in a game against the Seattle Seahawks. He lay there for a while while athletic trainers tended to him. Mason went back to the locker room and the 49ers said he was doubtful to return with a shoulder injury.

The good news was that Mason returned for the second half, although after just one carry he went to the sideline and moved his injured arm to get free. Isaac Guerendo came in when Mason left, and Patrick Taylor Jr. came in on the 49ers’ first drive of the second half when Guerendo needed rest. Mason didn’t return for the rest of that drive after making just one play. Mason did not return for the remainder of the third quarter.

Mason’s injury was concerning for the 49ers because they were already missing McCaffrey. Not many teams have a rock-solid third running back option on the roster, although the 49ers scheme seems to make everyone better. Rookie Guerendo is behind Mason on the depth chart. He’s an athletic fourth-round pick but had just 41 career yards before Thursday. Taylor is behind Guerendo. He hadn’t had a carry all season before Thursday. Deebo Samuel Sr. also takes shots at the tailback, but the 49ers wouldn’t want to turn him into a full-time tailback.

The 49ers might have missed McCaffrey in a few ways, but Mason had replaced most of his production. He was second in the NFL in rushing yards after five weeks, behind only Derrick Henry. Mason had 536 yards, over 100 yards more than any back other than Henry.

McCaffrey has been out of every game this season due to a calf/Achilles injury. He is expected to return sometime this season. The 49ers will hope Mason’s injury isn’t an issue before McCaffrey can return.