49ers RB Raheem Mostert to have season-ending knee surgery

In unfortunate news for 49ers fans, it appears running back Raheem Mostert won’t return in a couple of months after all. Instead, Mostert will have surgery on his knee that will sideline him for the rest of the season, he announced himself on Twitter.

In a responsive move, the 49ers will sign free agent running back Kerryon Johnson to their practice squad, Adam Schefter of ESPN.com tweets. Johnson, a 2018 second-round pick of the Lions, was cut by the Eagles last month. He also visited with the Raiders last week and is still only 24. Johnson operated as the Lions’ lead back for his first two years in the league but took a backseat to D’Andre Swift last year and was soon jettisoned.

Mostert says that he weighed his options and ultimately determined this was the best course of action. 49ers head coach Kyle Shanahan said Monday that Mostert would only undergo a scope for chipped knee cartilage, and he would return in about eight weeks. He’ll instead have cartilage repair surgery that will have a six-month recovery, Tom Pelissero of NFL Network tweets. That should at least give him plenty of time to be 100 percent for the start of 2022.

It looks like the backfield will now be Elijah Mitchell‘s to lead going forward. Mitchell got 19 carries in the 49ers’ win over the Lions after Mostert went down, turning them into 104 yards and a touchdown. Fourth-round rookie Trey Sermon, who was a healthy scratch in Week 1, could get a crack at some point as well.

It’s a tough blow for Mostert, who has been an extremely effective runner when healthy but has struggled to stay on the field. He’s averaged a ridiculous 5.7 yards per carry on 284 career attempts, but injuries limited him to eight games last year and held him back in prior years as well. It’s especially tough considering Mostert is in a contract year and will be an unrestricted free agent this spring.

It’ll be very interesting to see what kind of contract he lands in free agency. On the one hand he’s been remarkably efficient the past few years, but on the other hand has been plagued by injuries and has played in Shanahan’s system, in which virtually every running back seemingly thrives.