Sep 12, 2021; Detroit, Michigan, USA; San Francisco 49ers running back Raheem Mostert (31) puts a stiff arm to the helmet of Detroit Lions defensive back Will Harris (25) in the first quarter at Ford Field. Mandatory Credit: David Reginek-USA TODAY Sports

Raheem Mostert says he’s out for season; 49ers sign Kerryon Johnson

San Francisco 49ers running back Raheem Mostert announced on social media Tuesday that he has opted to undergo season-ending knee surgery following a Week 1 injury.

Mostert suffered chipped knee cartilage Sunday during San Francisco’s win over the host Detroit Lions. He was placed on injured reserve Monday, with coach Kyle Shanahan saying at the time that Mostert would receive an arthroscopic procedure and miss eight weeks.

ESPN reported Tuesday that the 49ers signed free agent running back Kerryon Johnson to bolster the position.

“Faithful, After consulting with multiple doctors and weighing my options, I will be having season-ending surgery to repair my knee,” Mostert wrote Tuesday. “This gives me, without a doubt in my mind, the best possibility at coming back 110%.”

Mostert left the Week 1 contest injured after taking two carries for 20 yards. His wife later claimed that Niners fans sent her “HUNDREDS, THOUSANDS” of abusive messages on social media, angry that the injury-prone Mostert was hurt again.

San Francisco ended up riding little-known rookie Elijah Mitchell for 104 rushing yards and a touchdown on 19 carries. The depth chart also includes third-round draft pick Trey Sermon, a healthy inactive on Sunday, and JaMycal Hasty.

Johnson joins that stable of backs with three years of experience (34 games, 16 starts) with the Detroit Lions. The former second-round draft pick was waived in May and claimed by the Philadelphia Eagles the next day, but the Eagles later waived him with an injury settlement.

–Field Level Media

Aug 29, 2021; Santa Clara, California, USA; San Francisco 49ers running back Raheem Mostert (31) runs the ball against the Las Vegas Raiders in the first quarter at Levi's Stadium. Mandatory Credit: Cary Edmondson-USA TODAY Sports

49ers RB Raheem Mostert departs after knee injury

San Francisco 49ers running back Raheem Mostert was ruled questionable to return after a knee injury in the first quarter of Sunday’s opener on the road against the Detroit Lions.

After rushing for 20 yards on his first two carries, the oft-injured Mostert was immediately removed from the game after the injury replaced by Elijah Mitchell, who ran 38 yards for a touchdown in the second quarter on his third carry.

JaMychal added a 3-yard TD run later in the second quarter as the 49ers built a 21-10 lead.

Despite being deemed questionable to return, Mostert he was loosening up on the sideline shortly after being replaced.

49ers rookie Trey Sermon, a former Ohio State star running back, was among the club’s inactives for the game.

–Field Level Media

October 11, 2020; Santa Clara, California, USA; San Francisco 49ers running back Raheem Mostert (31) is tackled by Miami Dolphins cornerback Xavien Howard (25) and strong safety Bobby McCain (28) during the second quarter at Levi's Stadium. Mandatory Credit: Kyle Terada-USA TODAY Sports

49ers’ Mostert (ankle) out against Saints

San Francisco running back Raheem Mostert will miss Sunday’s game against the New Orleans Saints, as he’ll remain on injured reserve with a high ankle sprain, 49ers coach Kyle Shanahan said Wednesday.

Mostert could return as early as Nov. 29, when the 49ers travel to play the Rams in Los Angeles. The 49ers have a bye next week.

Mostert landed on IR after suffering his injury in Week 6 against the Rams. The injury halted what had been a stellar start to the season for Mostert, who had 453 yards, including 303 rushing, and two touchdowns.

With Tevin Coleman (knee) also expected to miss this week, Jerick McKinnon and JaMycal Hasty will likely continue to split time in the backfield until Mostert’s return.

–Field Level Media

October 11, 2020; Santa Clara, California, USA; San Francisco 49ers running back Raheem Mostert (31) is tackled by Miami Dolphins outside linebacker Kamu Grugier-Hill (51) during the fourth quarter at Levi's Stadium. Mandatory Credit: Kyle Terada-USA TODAY Sports

Niners await evaluation on RB Mostert’s injury

An update on the injury to San Francisco running back Raheem Mostert isn’t expected until Monday at the earliest, coach Kyle Shanahan said after the 49ers defeated the visiting Los Angeles Rams on Sunday night in Santa Clara, Calif.

Mostert sustained a sprained left ankle late in the second quarter on Sunday, and finished the half with 64 yards on 16 carries. After having the ankle retaped at intermission, he returned for the third quarter, only to leave after one carry for one yard.

He also made two catches for 11 yards in the first half.

Mostert, who began the night with a team-leading 238 yards and one touchdown on 34 carries, was limping on the sidelines after exiting the game.

“We don’t know yet on Raheem,” Shanahan said. “I’m sure we’ll find out tomorrow.”

“I think Raheem has shown this league, starting last year, how special of a back he is,” Shanahan said. “Any time you lose a special guy like that, there definitely is a change. But I’ve also got a lot of confidence in our other guys too.”

Mostert missed two games earlier this season due to an ankle sprain.

Mostert rushed for 772 yards and eight touchdowns on 137 carries in 2019, and added 180 yards and two more scores on 14 catches.

JaMycal Hasty rushed for 37 yards on nine carries, including some runs as the Niners were chewing up the clock in the second half.

“I thought he did a real good job when he came in,” Shanahan said. “Hasty was up for the challenge, got some fresh legs in there, and I thought he gave us some juice a little bit. … Hasty got his opportunity and from what I saw, I thought he really helped us.”

–Field Level Media