49ers RB Raheem Mostert to miss 8 weeks with knee injury, CB Jason Verrett done for season

The San Francisco 49ers announced on Monday that cornerback Jason Verrett will miss the rest of the season with an ACL tear and running back Raheem Mostert is expected to miss eight weeks with a knee injury.

The news of Verrett's diagnosis confirms fears from Sunday's win over the Detroit Lions that the starting cornerback had suffered a season-ending right-knee injury after leaving the game in the first quarter. It's the latest devastating injury for Verrett, who tore his left ACL in 2016 and suffered an Achilles tear in 2018.

San Francisco is finalizing a deal for veteran free-agent cornerback Dre Kirkpatrick in the aftermath of Verrett's injury, according to NFL Network's Ian Rapoport.

Mostert to injured reserve

Mostert left Sunday's game after two carries and did not return. Head coach Kyle Shanahan told reporters after the game that trainers didn't fear that Mostert suffered an ACL tear but that he required further testing on Monday to confirm the nature of his injury.

On Monday, Shanahan told reporters that Mostert has chipped cartilage in his knee and will be placed on injured reserve. He expects him to return after around eight weeks.

DETROIT, MICHIGAN - SEPTEMBER 12: Raheem Mostert #31 of the San Francisco 49ers is tackled during the first half against the Detroit Lions at Ford Field on September 12, 2021 in Detroit, Michigan. (Photo by Gregory Shamus/Getty Images)
Raheem Mostert is expected to miss eight weeks with a knee injury. (Gregory Shamus/Getty Images)

Who will lead 49ers backfield?

Rookie running back Eli Mitchell took over as San Francisco's lead back after Mostert's exit, tallying 104 yards and a touchdown on 19 carries. Meanwhile fellow rookie Trevor Sermon missed the game as a healthy scratch. The 49ers drafted Sermon in the third round — three rounds ahead of Mitchell — and he was expected to have a significant role in the 49ers backfield this season.

Mitchell was the clear lead back on Sunday after Mostert's injury. He'll presumably continue in that role for the time being as Sermon's role remains a mystery. JaMycal Hasty carried the ball just once for three yards after Mostert's injury.