Trojans can’t just play out the spring

USC Coach Lane Kiffin and his returning players spent the last two months navigating their way through piercing criticism that followed the 2012 football season.

A team that featured a Heisman Trophy front-runner at quarterback opened No. 1 and then nose-dived to a 7-6 record and finished out of the Associated Press top 25.

Four coaches -- including three on defense -- resigned, moved on to other opportunities or were fired.

And a recruiting class that features seven early enrollees would have been stronger if several high-profile players had not broken commitments to USC and signed elsewhere.

So Kiffin and the Trojans are eager to start spring practice Tuesday, to begin looking forward.

USC will work out 15 times, concluding with a scrimmage at the Coliseum on April 13.

Eight practices -- March 5, 7, 14, 26 and 28 and April 4, 9 and 11 -- are open for public viewing from areas at nearby Dedeaux Field, though attendance will be limited to 200 per day. Practices begin at 4 p.m.

Here are the main questions facing the Trojans:

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Who will succeed Matt Barkley as the starting quarterback?

Max Wittek appeared on track after performing fairly well in the regular-season finale against Notre Dame. But Wittek struggled in the Trojans’ embarrassing Sun Bowl loss to Georgia Tech, opening the door for a real competition in spring practice -- the first at USC in four years.

Wittek and Cody Kessler are third-year sophomores, Max Browne a freshman who was tossing passes for Skyline High in Sammamish, Wash., three months ago.

The 6-foot-4, 245-pound Wittek passed for two touchdowns, with five interceptions, in his two starts.

Kiffin, inexplicably, did not turn to the 6-1, 215-pound Kessler during the Sun Bowl, so the Bakersfield native is eager to show what he can do.

And the 6-5, 215-pound Browne, who passed for 49 touchdowns with only five interceptions as a high school senior, is hoping to repeat what Barkley did four years ago when he became the first true freshman to start an opener for the Trojans.

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Can running backs Tre Madden and Justin Davis make an immediate impact?

The 6-1, 220-pound Madden appeared to make a smooth transition from linebacker to tailback last spring before he suffered a season-ending knee injury.

The third-year sophomore looked fit during bowl workouts in El Paso and, if sound, could provide a big-back presence.

Davis rushed for 1,806 yards and 23 touchdowns last season at Stockton Lincoln High and is among the early enrollees.

Senior Silas Redd, junior D.J. Morgan and sophomore Javorious Allen are returning tailbacks. Freshman Ty Isaac will arrive during the summer.

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Who will be the top receivers opposite Marqise Lee?

Sophomore Nelson Agholor is regarded as the front-runner to replace Robert Woods, who will be trying to make it in the NFL. Junior George Farmer hopes that his injury problems are behind him and that he can beat out senior De’Von Flournoy, sophomore Victor Blackwell and freshman Darreus Rogers for the No. 3 spot.

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Which linemen can earn playing time in key roles?

Junior Marcus Martin, who started 20 games at left guard the last two seasons, has been working at center to replace Khaled Holmes.

Junior Aundrey Walker and sophomore Max Tuerk shared time at left tackle last season but could also work at other spots. Redshirt freshman Zach Banner also figures to get reps at both tackle spots.

On defense, early enrollee Kenny Bigelow will be given an opportunity. Senior end Devon Kennard returns after sitting out last season because of a torn pectoral muscle.

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Are any freshmen capable of starting in the secondary?

Safety Su’a Cravens and cornerback Leon McQuay III are expected to get long looks in a defensive backfield that features no returning starters.

Cornerback Chris Hawkins, another early enrollee, will have plenty of opportunities in a competition that will include senior Torin Harris, sophomore Kevon Seymour and junior Anthony Brown.

Junior Josh Shaw, who started six games at cornerback last season, is expected to return to safety. Dion Bailey, a two-year starter at linebacker, had hoped to transition to safety, but the junior is recovering from shoulder surgery.

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Who are the new coaches?

Clancy Pendergast is the defensive coordinator and will coach the secondary. Former Indiana assistant Mike Ekeler will coach linebackers.

Former Kentucky assistant Mike Summers is offensive line coach and running game coordinator. Former Arizona Cardinals assistant Tommie Robinson has the unusual dual titles of running backs coach and passing game coordinator.

Quarterbacks coach Clay Helton, who is in his fourth season on the staff, was named offensive coordinator.

But Kiffin, the play-caller the last three seasons, has not said who will call plays.

That question, perhaps the biggest, probably won’t be answered until fall.

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gary.klein@latimes.com twitter.com/latimesklein