SALT LAKE CITY — Disaster has struck for No. 21 Utah.

That’s how coach Kyle Whittingham described the running back situation after the position was hit by injury yet again.

Starting running back Armand Shyne is done for the season after suffering an injury to his right leg during the 36-23 win over Arizona on Saturday. Shyne was promoted to starter last week and went down immediately after becoming the first Utes back to rush for 100 yards in a game this season. He finished with 101 yards and a touchdown on 19 carries.

Shyne will miss the spring session, also.

The sophomore was the fourth Utah running back to go down this season, and he wasn’t the only one Saturday. Junior Jordan Howard became No. 5 after making his debut at running back following Shyne’s injury. Whittingham didn’t specify the injury, but Howard cannot play this week against Oregon State.

Game 1 starter Joe Williams retired after two games due to injuries.

“We’re down to our sixth running back now, I guess you could say,” Whittingham said. “It’s been a little bit of a mystery this year as far as the injuries. But you just deal with it and move on. We’ll figure it out. Don’t have an answer for you right now. We will have answer very soon.”

Where that answer will come from may be more of a mystery. Freshman Zack Moss will be a game-time decision after missing the last game and junior Troy McCormick also missed last week. Shyne, Moss, McCormick and Williams have combined for 88.2 percent of Utah’s rushing yards this season.

Whittingham said they’re exploring all options. The coaching staff is considering a position switch for someone who has previous experience at running back in high school or junior college. Reaching out to Williams to see if he could un-retire is even on the table.

The play-calling is likely to be affected, also.

“That will come into play as well,” Whittingham said. “Maybe more the quarterback-run game as well. We just have to look for any and all answers because right now it’s a pretty desperate situation at running back.”

Moss is listed atop the depth chart this week, but there’s no certainty that he’ll be available. Redshirt freshman Marcel Manalo is listed as No. 2, but last game was his first career action and he still hasn’t had a carry. Freshman Devonta’e Henry-Cole will get practice reps this week as coaches decide whether to pull his planned redshirt.

“When you’re in redshirt mode, if disaster strikes, which disaster has struck, then you’ve got to re-think things,” Whittingham said.

Quarterback Troy Williams knows some of the offensive load could be shifted to his arms, and maybe his legs. The Utes are historically a run-first team and have 262 rushing attempts compared to 198 pass attempts.

That could start to skew in the other direction. Troy Williams was ranked by as the No. 1 dual-threat quarterback in the nation coming out of high school in 2013, so Utah could utilize his mobility more than in previous games. He has 92 rushing yards and three touchdowns on 41 carries this season.

“I’m willing to do whatever it takes to help my team win games,” he said. “If that means I have to run the ball more, then so be it. I have no problem taking on that role. We may have to make a couple of tweaks here and there, but I’m sure we’ll stick with what has been working all season. … We just have to do a little more as an offense, period.”

Injuries to the backs aren’t the only challenges for the run game. Center J.J. Dielman, a three-year starter, was lost for the season two weeks ago and backup Lo Falemaka was unable to play against Arizona because of a leg injury. Senior Nick Nowakowski got the start.

The Utes have also lost defensive end Kylie Fitts and tight end Siale Fakailoatonga to injuries. Other starters on the defensive line, in the secondary and at receiver have also missed games due to injury.

“Worst I can remember,” Whittingham said. “I’ve been in it a lot of years and I cannot remember a year with this many injuries. The sheer amount of injures that we’ve had.”