Roy Helu burst up the middle, knifing through the Iowa State defense for a 14-yard gain.

You know what happens next.

Helu, the Nebraska junior running back, lost possession of the football at the Iowa State 1-yard line. An official replay review confirmed the fumble, which Michael O’Connell recovered in the end zone.

That was with 9 minutes, 22 seconds remaining in the third quarter. Helu, who also lost a fumble on the game’s first play, didn’t carry the ball again in Nebraska’s 9-7 loss at Memorial Stadium.

In fact, he didn’t return to the field until late in the fourth quarter, on Nebraska’s second-to-final series, when he caught a screen pass from Zac Lee.

Did Helu’s absence have anything to do with his two lost fumbles?

“Yeah. He’s not hanging on to the ball,” Nebraska running backs coach Tim Beck said. “Might as well try someone else, right? There’s a bunch of guys on scholarship, so we’ll see how they do.”

So Beck turned to true freshman Dontrayevous Robinson, who carried five straight times on Nebraska’s next series for gains of 2, 7, 7, 7 and 13 yards … and a lost fumble at the Iowa State 5.

“I thought he played pretty well, except for the fumble,” Beck said of Robinson, who also played in the first half and finished with 15 carries for 77 yards. His longest run was 21 yards.

“He ran hard,” Beck said. “I don’t know. Just watching him, I thought he did a pretty job for his first time.”

Beck seemed less forgiving of Helu, who fumbled two of the five times he carried the ball. His first fumble led to an Iowa State field goal. His second killed what looked to be a go-ahead touchdown drive.

Helu has been bothered by a sore shoulder and practiced last week with a no-contact green jersey.

No excuses, Beck said.

“You can speculate all you want with that stuff,” Beck said. “He played last game (against Texas Tech) with his shoulder and didn’t fumble.

“I don’t know. He’s got to hang on to the ball, man. That doesn’t matter. If he can’t do it, then we’ve got to find someone else. That’s the bottom line. We’ve got to hang on to the ball. We can’t beat anybody turning the ball over eight times.”

Nebraska’s five lost fumbles were its most since the Baylor game in 2001, and the seven fumbles were its most since the Kansas State game in 2005. The Huskers won both games.

Nebraska gained 114 yards on 28 carries against Iowa State — an average of 4.1 yards per rush.

“Our offensive line did a great job today,” Beck said. “Absolutely great job. Smashed them all over the place. There were some big-(old) holes in there for guys to run.

“We have to be able to convert. It’s frustrating when you play a game like that.”

Helu and Robinson both declined interview requests.

Nebraska began its search last week to replace No. 2 running back Rex Burkhead, who’s out indefinitely with a foot injury. Austin Jones and Marcus Mendoza filled that role against Texas Tech, while Robinson burned his redshirt in that game, but by playing only on special teams.

Beck said he’d planned on playing Robinson at running back, too, but Nebraska’s 21-3 deficit last week negated that possibility.

“That kind of limited him a little last game. We were in some two-minute situations last game, some signals and everything,” Beck said.

“You’ve got to learn to walk before you can run. He was in a walking pace last game, and if last game had warranted a walking pace he probably would’ve played more last game.”

Reach Brian Rosenthal at brosenthal@journalstar.com or 473-7436.