Raheem Mostert Injury Update: 49ers RB out for the season with knee injury

49ers RB Raheem Mostert left with a knee injury early in the first quarter in Week 1. How long could he be out of the starting lineup?

San Francisco 49ers running back Raheem Mostert is dealing with yet another injury that threatens to keep him out of games. What updates are there on the injury, and how much time could Mostert miss?

Update 9/14/21: Raheem Mostert announced on social media that he would be having season-ending knee surgery.

Raheem Mostert leaves Week 1 contest with knee injury

Mostert left the 49ers’ 41-33 victory over the Detroit Lions with what Kyle Shanahan called chipped cartilage. The timeline for his return is eight weeks.

“They told me they’re not worried about it being an ACL, so that’s obviously real good news. But that’s about all we know,” San Francisco coach Kyle Shanahan said Sunday.

The ensures that Mostert, who also dealt with a knee injury during OTAs, will again miss at least one game due to injury — as he has in three of the previous four seasons. Assuming Mostert sticks to the project rehab schedule, the soonest he could return is the Cardinals’ Week 9 game against the San Francisco 49ers.

Long history with injuries

Mostert has dealt with knee, ankle, calf, and arm issues in recent years. The ailments have been a major reason he has appeared in just 59 of a possible 102 games in his career.

On Sunday evening, his wife claimed that his long injury history made Mostert the target of some pretty vile social media abuse following the game.

Mostert logged just 4 snaps and appeared to get hurt in San Francisco’s second series of Sunday’s win. He rushed twice for 20 yards on that possession but left the field shortly after and did not return.

The 49ers decided pre-game to make rookie Trey Sermon a healthy scratch, so Mostert’s departure left the Niners with just two available running backs — Elijah Mitchell and JaMycal Hasty.

Mitchell made the most of that opportunity by rushing for 104 yards and a touchdown on 19 carries in his NFL debut. The 49ers selected Mitchell with the 194th pick in the 2021 NFL Draft. The Louisiana product was the 10th running back off the board.

Mostert’s fantasy outlook

Mostert’s situation has many fantasy football managers scratching their heads. He left the 49ers game against the Lions with a knee injury. Mostert was then deemed questionable to return, but was later ruled out. This was shocking considering he was recommended as a start in Week 1 by many in the industry.

It is unclear when Mostert suffered the injury. He had 20 rushing yards on two attempts prior to leaving the field. The 49ers have one of the most robust running games in the NFL. Mostert is a must-start when active. However, head coach Kyle Shanahan is very coy regarding how the touches will be distributed.

San Francisco only dressed three running backs on Sunday, including Mostert. The team only has JaMycal Hasty, rookies Elijah Mitchell, and Trey Sermon to carry the load. It will be fascinating to see which one gets the most carries while Mostert is sidelined. All fantasy managers can do now is wait until we learn more information.

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