USC’s biggest goal for spring football may be finding out who replaces Sam Darnold at quarterback

Clay Helton led USC to double-digit victories in his first two years as coach.

But now the question looms: Can Helton and the Trojans maintain success without star quarterback Sam Darnold?

USC won the Pac-12 Conference title last season before stumbling in a lopsided loss to Ohio State in the Cotton Bowl.

This winter Helton’s contract was extended through 2023, and he followed the announcement by delivering a top-rated recruiting class.

“All of them are going to represent USC and take the next step to championships,” Helton said on national signing day in February. “And that’s our ultimate goal.”

Whether USC will improve on last season’s 11-3 mark and make a run to its first College Football Playoff berth remains the subplot to the biggest question facing the Trojans when they open spring practice Tuesday.

Who will play quarterback?

Here are the other big questions for the Trojans:

Which quarterback will emerge?

Third-year sophomore Matt Fink spent the last two seasons studying Darnold, a two-year starter who is projected as a top-five pick in the NFL draft.

Fink, from Glendora High, is the only quarterback on the roster with college experience and it is limited.

Fink has played in three games, completing six of nine passes for 43 yards.

Jack Sears followed Darnold to USC from San Clemente High. A former four-star recruit, Sears was a redshirt last season.

Regardless of which quarterback emerges this spring, the competition likely will continue into the fall and will then include freshman J.T. Daniels, a highly regarded recruit who led Mater Dei to a 15-0 mark last season.

Daniels is graduating high school a year early to enroll at USC.

Helton said on signing day that Daniels, the 2017 Gatorade player of the year, was “probably smarter than the head coach and the quarterback coach” at USC.

How do you replace Ronald Jones II?

Tim Drevno, who coached USC’s offensive line in 2014, will return to coach running backs after spending three seasons as Michigan’s offensive coordinator.

That much we know.

Still up for debate is who will supplant Ronald Jones II as USC’s top rusher.

Jones made himself available for the NFL draft after he rushed for 1,550 yards and 19 touchdowns as a junior last season.

His understudy, sophomore Stephen Carr, will be sidelined for spring practice after undergoing back surgery.

Senior Aca’Cedric Ware and sophomore Vavae Malepeai will get the bulk of the carries.

Is there a playmaker up front on defense?

Outside linebacker Uchenna Nwosu and lineman Josh Fatu exhausted their eligibility and lineman Rasheem Green departed for the NFL draft with eligibility remaining.

A sizable void remains in their absence: Green had 10 sacks last season and Nwosu had 9½.

Junior Oluwole Betiku is a likely candidate to replace Nwosu. But he will be sidelined for spring practice after undergoing hip surgery.

Sophomore Juliano Falaniko and redshirt freshman Hunter Echols will compete at the position.

Outside linebacker Porter Gustin, who was sidelined for most of last season because of toe and biceps injuries, will return.

A host of players with experience will compete to replace Fatu and Green, including fifth-year senior Malik Dorton, junior Christian Rector and sophomore Brandon Pili.

Which young receivers will emerge?

Deontay Burnett arrived at USC three seasons ago as an unheralded recruit from Gardena Serra. After he starred in the 2017 Rose Bowl, then caught 86 passes for 1,114 yards and nine touchdowns last season, the standout receiver has made himself available for the NFL draft.

Gone also is the sure-handed Steven Mitchell Jr., who exhausted his eligibility.

Third-year sophomore Tyler Vaughns, who caught 57 passes for 809 yards and five touchdowns last season, is the likely candidate to elevate to the top receiver.

And junior Michael Pittman Jr. is expected to take on a larger role after starting five of the final six games last season.

Fifth-year senior Jalen Green is no longer on the roster and neither is Joseph Lewis, who was arrested last month on suspicion of domestic violence.

But USC has several young receivers who are expected to contribute.

Third-year sophomore Velus Jones Jr., a kickoff returner last season, will take on a larger role.

Trevon Sidney, Josh Imatorbhebhe, Randal Grimes and Keyshawn Young also will compete for spots.

Who will take over at center?

The Trojans return four of their five starting offensive linemen.

Depth is not a concern. Experience will be.

Gone is center Nico Falah, who started every game in his fifth season with the program. And Falah’s backup, Cole Smith, is no longer on the roster.

The Trojans might have to turn to redshirt freshman Brett Neilon to fill the role.

Fifth-year senior Toa Lobendahn, who has played four positions on the line, could return to center from left tackle — giving way for Austin Jackson or Clayton Johnston to protect a young quarterback’s blind side.

Fourth-year junior Roy Hemsley, a probable backup to left guard Chris Brown, announced last week that he would transfer to Arizona State and Nathan Smith, who was buried last season on the depth chart at right tackle, is no longer on the roster.

lindsey.thiry@latimes.com

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