There’s talent among USC’s linebackers, but how they play as a group remains to be seen

Justin Davis flitted to his left on a third-down run Wednesday, probing for the edge. It was in vain: Outside linebacker Porter Gustin had rammed his blocker two yards into the backfield.

Davis stuttered and scanned. Behind him, the offensive line had paved a hole through the defensive front, so he turned and burst toward it. That was a mirage, too: The other outside linebacker, Uchenna Nwosu, was stalking, ready to close the gap.

Davis had nowhere to go, his would-be first down snuffed out by USC’s linebackers.

That group, with Gustin and Nwosu on the outside and Michael Hutchings and Cameron Smith on the inside, has made the Trojans’ run defense less of a liability during training camp, despite a young, thin defensive line.

“That’s four really solid players that have played a lot of football,” Coach Clay Helton said. “And that experience is showing.”

USC’s linebackers, a unit stuffed with talent but saddled with new personnel and a new scheme, might be the team’s most important group. It is responsible for reinforcing the line, and cleaning up its messes. But after a major off-season makeover, it is also, perhaps, its biggest mystery.

The rest of USC’s defense has been easier to judge. The biggest question concerning the secondary is whether it’ll be among the best in the nation or just the Pac-12 Conference. And even the coaching staff expects the line to weather some tough early matchups. But the best- and worst-case scenarios for the linebackers occupy a much wider range.

During training camp, the unit has solidified into what Helton believes is a strength. More often than not, it has suffocated USC’s offense in team run drills.

On Saturday, for instance, USC placed the ball near the goal line and blasted artificial crowd noise from two large speakers. One of the best offensive lines in the nation dug in. Two talented backs took handoffs. Three times out of four, the play ended with the defensive reserves mobbing the field, squirting water bottles in the air, celebrating a stop powered by the linebackers.

“We have some great players, guys that have improved tremendously from the spring,” Hutchings said.

There were significant losses in the linebacker group after last season. Starters Scott Felix and Anthony Sarao graduated and Su’a Cravens left a year early for the NFL. The only returning starter, Smith, was recovering from major knee surgery.

New defensive coordinator Clancy Pendergast reintroduced the 5-2 defense upon his arrival, a scheme fairly similar to the 3-4 already in place, but with new responsibilities to learn.

Gustin said during the spring, those factors combined to create sluggish, tentative play at times.

Still, USC had talent. Gustin, who plays with his shorts rolled up to the middle of his thighs, his jersey rolled up above his navel and who seems to arrive at each practice wearing less and less fabric, is an imposing force at 6 feet 5 and 260 pounds.

Nwosu has started only once, but he has been a game-leader in tackles. Hutchings, a senior, pilots the unit.

And Smith, who is nearing a full return, was on track to become the first freshman to lead USC in tackles before his injury last season. (He was also the team’s leader in interceptions at the time.) He has participated in team drills in training camp but is occasionally removed as a precaution. Helton compared that to “caging a lion.”

Phil Steele’s College Football Preview ranked USC’s linebackers 19th best in the country. Learning to play in the defense and with each other, Nwosu said, “was just a matter of time.”

Players say the 5-2 defense allows them to react more aggressively, to attack more. Helton said it better disguises blitz packages and confuses quarterbacks. That will be essential: USC plans to stack the box often this season to bolster the defensive line in the run game. If there is no pressure, the secondary will be vulnerable.

There have been hiccups. In Wednesday’s practice, the offense shredded the defense on the ground during its up-tempo period. The good news is that Alabama and Stanford, two of USC’s first three opponents, prefer a more plodding pace.

The bad news, of course, is that USC probably won’t face two better running teams. Gustin admitted that, earlier in training camp, film of USC’s practices augured a bleak start.

Then, Gustin said, something clicked. Confidence abounded. The film suggested strength.

“We all realized it,” Gustin said. “You could see it.”

Quick hits

Quarterbacks Max Browne and Sam Darnold both played crisply Wednesday. Darnold “had an unbelievable day today,” Helton said. ... Helton confirmed that all players are academically eligible. … Damien Mama (ankle), Stevie Tu’ikolovatu (hip) and Rasheem Green (knee contusion) were pulled from practice. … Ykili Ross (stomach illness), Cole Smith (stomach illness), Jordan Simmons (knee), Isaiah Langley (concussion protocol) and safety John Plattenburg (concussion protocol) did not practice.

zach.helfand@latimes.com

Twitter: @zhelfand