Frustration grows as USC’s offense struggles during scrimmage

Sam Darnold ripped off his chinstrap and jogged straight to the sideline. A few minutes later, he jogged straight to the sideline again. He ripped off his chinstrap with a little more force. A few minutes after that: same thing, this chinstrap ripped with even more vigor.

The scene repeated itself over and over on Saturday, when USC ran a 70-play scrimmage. The defense looked scary. The offense looked ugly. Darnold would run three plays, rip off his chinstrap and run straight to the sideline, the frustration growing increasingly evident even for the usually unflappable quarterback.

The Trojans’ first-team offense ran eight drives. They had one first down, one interception and six three-and-outs.

One of those three-and-outs actually resulted in a safety, but for the sake of extra repetitions, USC lined back up for a third down anyway. That attempt, too, failed.

Afterward, coach Clay Helton said the defense played “lights out” but added, “it was good to see the reality today.”

The reality is, USC’s offense could not move the ball. The running game found little space. Darnold threw erratically — one pass air-mailed his target by several feet. The secondary manhandled his pass catchers.

The absence of tight end Daniel Imatorbhebhe, who has been sidelined because of an injured hip flexor, neutered USC’s tight-end game, and USC’s receivers found little space. Several Darnold passes were placed well, but his target had been forced off his route.

USC’s lone touchdown came during a red-zone period, when Ronald Jones punched in a short run. In the same period, a pass with too much loft facilitated a one-handed interception by Ajene Harris. A mushy route by Deontay Burnett didn’t help.

It is not unusual for the defense to dominate the first scrimmages of training camp. The offensive playbook is typically more sophisticated and provides a steeper learning curve. During a game week, coaches typically whittle down the playbook to a more manageable size.

“Once we get into playbook mode and that whole bible becomes just one specific game plan, I think it’s gonna help them a bunch,” Helton said.

And the Trojans’ defense is indeed experienced, with a front seven capable of owning the line of scrimmage. “I thought they came with an attitude,” Helton said.

Helton said outside linebackers Porter Gustin and Uchenna Nwosu were “phenomenal” and cornerback Iman Marshall “had probably his best practice of camp.”

But Saturday’s scrimmage raised several concerns, the same ones that have lingered since the offseason: Can the receivers, without JuJu Smith-Schuster and Darreus Rogers, get open for Darnold? Can the line open holes for running back Ronald Jones II?

“Obviously we’ve got a lot of work to do,” Helton said.

Kicking woes continue

The volume on both sidelines dropped about midway through the field-goal portion of the scrimmage. By the end of it, USC’s players had gone quiet.

Everyone was watching the kickers. Neither could hit with any consistency.

Mike Brown made two of six attempts, his two successful tries about 40 yards and from about 45 yards. Chase McGrath made one of three, from about 40 yards.

“It was not a very good outing by either one,” Helton said. “We’ve got a lot of work to be able to do, just being honest there.”

Brown and McGrath have each had better days during training camp. But the outlook was bleak enough that Helton broached the idea of a more aggressive fourth-down approach.

Faced with a fourth down and four yards to go, or a long field goal, Helton said USC may have to opt to go for it.

“If it doesn’t improve,” he added.

Quick hits

Imatorbhebhe ran without a setback this week. Helton said he hopes to have him within the next one to two weeks. … Running back Aca’Cedric Ware sprained his shoulder. Helton does not expect him to miss significant time.

zach.helfand@latimes.com

Follow Zach Helfand on Twitter @zhelfand