Nov 21, 2015; Eugene, OR, USA; USC Trojans linebacker Olajuwon Tucker (34) and linebacker Porter Gustin (45) defend as Oregon Ducks quarterback Vernon Adams Jr. (3) runs the ball at Autzen Stadium. Mandatory Credit: Scott Olmos-USA TODAY Sports

USC football will be replacing three starters at linebacker in 2016, but there’s a strong mix of young stars and overlooked veterans looking for a chance to shine.

Despite fielding just one senior starter in USC’s linebacker corps in 2015, circumstances have left the Trojans with a single returning starter and questions around all four spots.

On top of that, the promotion of Peter Sirmon to defensive coordinator at Mississippi State means the unit will be in the hands of new coach in 2016.

Former running backs coach Johnny Nansen has jumped back over to defense to coach the linebackers, hoping to get as much out of that group as he was able to achieve with the Trojan rushers.

He’ll need to act quickly, as USC will face an Alabama squad out to test the rebuild front seven on the first day of the season.

Who’s back: Joel Foy (JR), Porter Gustin (SO), Don Hill (SO), John Houston (RS-FR), Michael Hutchings (SR), Osa Masina (SO), Grant Moore (SO), Uchenna Nwosu (JR), Quinton Powell (SR), Jabari Ruffin (RS-SR), Cameron Smith (SO), Olajuwon Tucker (JR)

Who’s gone: Su’a Cravens, Lamar Dawson, Scott Felix, Anthony Sarao

Who’s new: Oluwole Betiku, Jordan Iosefa

A rebuild is required…

Three of USC’s four linebacker spots lost starters at the end of the 2015 season.

Su’a Cravens opted to leave early for the NFL, Anthony Sarao graduated and Scott Felix was declared ineligible for his final season.

Moreover, Smith, the one returning starter for USC at linebacker, hasn’t put on pads in eight months.

Losing Cravens is a particular blow considering his hybrid ability. The versatility to line Cravens up close to the line of scrimmage or as a deep safety as needed was a help to the Trojans as injury trouble hit. USC won’t have that luxury this year.

SEE MORE: Su’a Cravens’ Top 5 Moments At USC

In Sarao they’re losing a steady, if unspectacular, presence at weakside linebacker who accounted for 59 tackles in 2015.

As for Felix, he logged five and a half tackles for loss, including four sacks, last year and would have been a veteran head in a young defensive front in his final season.

…But they’re reloading with added firepower

There’s good news though. Much like the defensive line, the Trojan linebackers are primed to bring in upgrades at all but one of those positions.

There’ll be no replacing Su’a Cravens in terms of total impact on the defense, but the role of the strongside linebacker, labeled defensive end, in Pendergast’s system appeared to suit Uchenna Nwosu in the spring well enough that Cravens’ absence shouldn’t be glaring.

Nwosu came to USC as a bit of a hybrid player to begin with, so there should be some flexibility in his role as well.

Behind him, five-star prospect Oluwole Betiku and fellow freshman Jordan Iosefa will have a chance to learn the ropes.

In the other positions, there is clear potential for improvement in athleticism and production.

At the rush end spot, now designated as a defensive end, Felix was often in the right place but prone to missing tackles and always seemed one step short of making a real impact. Gustin, on the other hand, had the look of an impact player from the moment he stepped on the Coliseum floor.

For whatever reason Felix was favored to Gustin early in the season but the young challenger earned starts ahead of his more veteran teammate against UCLA and Stanford, the second time around. He also led the team in sacks.

With Felix sidelined, Gustin looks ready to take on the role in which Morgan Breslin and J.R. Tavai thrived during the 2013 season as a pass rushing specialist.

SEE MORE: 5 Most Physical Trojans For 2016

In the middle, the Trojans will need Smith come back from his ACL tear no worse for wear. If he does, that position will be set for foreseeable future.

As a plus, Michael Hutchings was able to prepare with first team reps for much of the spring. If Smith isn’t ready to go, USC will lean on the senior to live up to the promise he showed early in his career. If Smith is back to 100%, the Trojans will have a dependable back up in place.

Replacing Sarao is a bit more tricky.

There is a free-for-all of players hoping to step into the second inside linebacker role, including Hutchings, Quinton Powell, Olajuwon Tucker, and promising youngsters Osa Masina and John Houston.

Powell appeared to have an advantage at the spot during the spring, but Tucker earned three starts in place of Smith last year and won’t concede easily.

Meanwhile, Masina and Houston have both made the move inside from outside spots last year and were projected as top recruits a year ago.

Masina would give the Trojans a strong physical presence against the run while Houston, who redshirted last year while dealing with injury, is more capable in coverage and could be a valuable player in the pass-happy Pac-12 if he comes along quickly enough.

Quinton Powell’s revival?

Bleacher Report named Masina as one of their predicted breakout players at linebacker for the 2016 season, which isn’t a bad shout considering the hype he commanded coming out of high school.

While it would be no surprise to see Masina take the next step up in his development this season, it’s the revival of Quinton Powell’s career under Clancy Pendergast that carries the most intrigue.

Powell raved about the changes implemented in Pendergast’s system throughout the spring and continues to sing praises for the more attacking style this summer.

SEE MORE: 5 Takeaways from USC’s 2016 Spring Camp

That confidence in the coaching he is receiving, his role on the team and the philosophy of the defense as a whole resulted in an impressive camp showing.

After two years of going the wrong way under Justin Wilcox, Powell may turn out to be the player who benefited most from the assistant coaching changes made last December.