The San Francisco 49ers have been injury-plagued this season and Thursday night's 34-3 victory over the Oakland Raiders was no different. This time, the running back group was impacted again.

The team is already without Jerick McKinnon, who was supposed to be the featured back in head coach Kyle Shanahan's offense. Running back Matt Breida has been battling various injuries since the preseason. Now, San Francisco will be moving forward without backup running back and special teams standout Raheem Mostert for the remainder of the season.

Head coach Kyle Shanahan announced that the running back would have surgery on his fractured right forearm on Friday and be placed on injured reserve.

"I wasn't told how long [the recovery] would be," Shanahan told reporters on Friday. "I know he's going on IR. He's out for the year but I'm sure he'll be fine by next year. It's a broken bone, different ligaments, and things like that."

Mostert left Thursday's game with 4:38 left in the third quarter after rushing the football seven times for 86 yards, including a 52-yard score — the first touchdown of his career. He left the field for the locker room with his arm in an air cast and did not return.

Shanahan already assumed he would be lost for the remainder of the season due to the severity of the injury.

"They didn't tell me," Shanahan said after the game, "but I would assume so with a broken arm."

Mostert was having his best NFL season rushing the football while averaging a career-high 7.7 yards per attempt. He finished the season with 34 carries for 261 yards while adding six receptions for 25 yards. Over the past four games, Mostert has averaged 8.9 yards per carry in limited action. He was averaging 12.3 yards per carry on Thursday night before the injury.

The Philadelphia Eagles signed Mostert as an undrafted free agent out of Purdue in 2015. He spent time with the Miami Dolphins, Baltimore Ravens, Cleveland Browns, and Chicago Bears before signing with San Francisco on November 28, 2016.

Shanahan also told reporters that cornerback Emmanuel Moseley dislocated his shoulder and will have surgery on Tuesday. He too will be placed on injured reserve. Moseley was promoted from the practice squad before Thursday night's kickoff.