Fletcher Cox, Mychal Kendricks, Vinny Curry and Brandon Boykin have been through a lot in their short tenure with the Eagles. They were all rookies on defense last season and experienced varying degrees of success. Kendricks, a second-round pick, started all but one game at outside linebacker but wore down as the season went along. Cox, the first-round pick at defensive tackle, slowly developed into a reliable starter. Curry, another second-rounder at defensive end, struggled to get on the field and make an impact when he did. Boykin, a fourth-rounder, had an up-and-down season as a slot cornerback. It’s supposed to get easier now that each has a full season under his belt. The reality is that all four players are playing for their third coach and their third defensive system in three seasons (including their senior years of college). The defensive system of head coach Chip Kelly and coordinator Bill Davis is much different than that of Andy Reid. “It’s all about being professional about it,” Cox said. “And being coachable and dealing with the situation as best you can, knowing it’s a business.” Cox is playing both defensive tackle and defensive end under Davis’ hybrid 3-4 front as opposed to strictly playing defensive tackle last season. Curry is playing defensive end and also getting snaps at outside linebacker. Kendricks is moving to inside linebacker, while Boykin is getting chances both at slot corner and on the outside. “I did the same thing in college, moving around a whole lot,” Cox said. “Defensive end, defensive tackle – it didn’t matter where I was. ... That’s the most fun part about it. I get to see a lot of different looks, not just the same look inside.” Cox didn’t start last season until the seventh game. But he still tied for the team lead in sacks with 5.5, ranking fifth among all rookies and fifth among all defensive tackles.