Kyle Shanahan says Raheem Mostert broke his arm, is likely out for the season

Raheem Mostert carried the football seven times for 86 yards before being tripped up by Oakland Raiders defensive tackle Clinton McDonald in the third quarter and going down with what appeared to be a gruesome arm injury. He screamed on the field while teammates and Raiders players gestured to the sidelines for help.

Mostert was eventually able to leave the field and headed to the locker room with his arm in a brace. He was, obviously, ruled out for the remainder of the game.

Head coach Kyle Shanahan confirmed after the game that Mostert fractured his right forearm and will likely miss the remainder of the season. It's another injury to add to the list for a team that has been plagued with them this season.

"They didn't tell me, but I would assume so with a broken arm," Shanahan responded when asked if the injury was season-ending.

Mostert was having his best NFL season rushing the football while averaging a career-high 7.7 yards per attempt. He likely finishes the season with 34 carries for 261 yards while adding six receptions for 25 yards. Mostert had his first career touchdown during Thursday night's 34-3 victory over the Raiders.

The 49ers will likely add another running back to the active roster. The team has Matt Dayes and Jeff Wilson on the practice squad.