LOUISVILLE, Ky. (AP) — Louisville returns just four starters from the nation’s sixth-ranked defense last season but the Cardinals might not miss a beat this year with those key players and a mix of regulars among their front seven.

Coach Bobby Petrino called the group the core of his team during Saturday’s media day activities.

Petrino announced that three of those returning starters — linebackers James Burgess and Keith Kelsey and defensive lineman Sheldon Rankins — were voted captains by their teammates and coaches, joining running back Brandon Radcliff and offensive lineman Aaron Epps

Burgess and Rankins were voted to the preseason All-ACC squad last month. Rankins led the team in sacks last season with eight and had a career-best 13.5 tackles for loss, earning third team All-ACC honors before passing on the NFL draft to return for his senior year. Fellow senior Burgess has had 71 tackles in each of his two seasons as a starter, adding four sacks and three interceptions last year. Kelsey, a junior, was second on the team with 87 tackles in his first year as a starter.

“I think when you look at what our biggest strength is, certainly it’d be our front seven,” Petrino said. “We have guys with really good talent, a lot of experience and really good students of the game.”

Defensive lineman Pio Vatuvei also returns as a starter, along with another regular contributor upfront in D’Angelo Brown. Keith Brown, a freshman All-America at linebacker before being slowed by injuries the past two years, is expected to start, and the Cardinals also add junior college transfer Devonte Fields, the Big 12 defensive player of the year as a freshman at TCU in 2012.

Fields enrolled at Louisville on Aug. 4 after a 2014 domestic violence case against him was dismissed in June, following the completion of an anger management course. Petrino said Saturday that Fields arrived out of shape and must improve his conditioning before he’ll have a chance of breaking into the depth chart.

Last year’s defense gave up just 310 yards a game and the Cardinals lost six starters to the NFL. Louisville must replace a secondary that led the country in interceptions last year but with Petrino choosing between five players at quarterback and needing to settle on two new starters at receiver and a reworked offensive line, this year’s defense is still the more experienced side of the ball.

“The first thing I worry about when having a young offense is trying to do too much,” Petrino said. “What we have to figure out here in the next week and a half is what it is that we can learn and execute.”

Rankins said that doesn’t put any extra burden on the defense, even with the Cardinals facing Auburn in their opener on Sept. 5

“With our young offense, I know Coach Petrino will do what’s best for them,” Rankins said. “If that means bringing them along slowly, he’s going to do that. But he’s also going to put them in the right position to make plays and help us win the game. It’s not just going to fall on us.”

Burgess echoed his fellow captain, saying the defense was motivated by having an “offensive guru” as their coach.

“The more stops we get, the more chances he has with the ball in his hands,” Burgess said of Petrino. “We know that if we keep giving him stops that eventually he’s going to put points in the board.”