AP FILE PHOTO - West Virginia’s CJ Donaldson Jr. (12) tries to break away against Texas Tech during the second half of their Big 12 Conference football game Oct. 22 in Lubbock, Texas.

MORGANTOWN, W.Va. — West Virginia running back CJ Donaldson will miss the rest of the season after undergoing surgery, coach Neal Brown said Tuesday.

Brown didn’t specify the type of injury to Donaldson, who hurt his lower leg in a 41-31 loss to No. 7 TCU on Saturday. It was the second time the 240-pound freshman was injured this season.

Donaldson went into the concussion protocol after a loss at Texas on Oct. 1. He sat out a win over Baylor on Oct. 13, then returned the following week at Texas Tech. Donaldson had four 100-yard rushing games this season. He has a team-high 526 yards with eight touchdowns.

West Virginia’s backfield is already thin. Tony Mathis sat out the TCU game and his status for this week remains to be determined. Backup Justin Johnson has been banged up and Brown hopes he can play. Redshirt freshman Jaylen Anderson, who had three carries against TCU, will likely see more action.

West Virginia (3-5, 1-4 Big 12) plays at Iowa State (3-5, 0-5) on Saturday.