Philadelphia Eagles positional reviews: Tackle Fletcher Cox must continue to show why he's the defense's foundation piece

Philly.com has been looking at the Eagles' 90-man roster since last Monday, before they begin organized team activities on May 23. Here's the schedule:

May 8: Wide receivers
May 9: Running backs
May 10: Offensive linemen
May 11: Tight ends
May 12: Defensive ends
May 15: Defensive tackles
May 16: Linebackers
May 17: Cornerbacks
May 18: Safeties
May 19: Quarterbacks

DEFENSIVE TACKLES

Spotlight on: Fletcher Cox

Entering the 2016 season, Cox was in the spotlight after earning his first Pro Bowl appearance, signing a $103 million contract and transitioning to a 4-3 defense that figured to further showcase his elite talent.

By most objective standards, Cox had a good year – 43 tackles, 6.5 sacks, one forced fumble, another Pro Bowl bid. But the statistical production dipped from the year before. By his own admission, Cox "hit a wall" after winning defensive player of the month in September. Four of his sacks came in the first four games, and he had an eight-game stretch in which he didn't take down the quarterback. He was often the focal point of the opposing offensive line's game plan, seeing double teams weekly.

"I talk with my position coach and he says, 'That comes with it,' " Cox said last November. "I get a slide a lot, and he's telling me to get a set of hands off me and keep pushing. If two people are on me, that means three other guys are getting one-on-ones. And when I do get those one-on-ones, I have to win."

The Eagles need top production from Cox if they're going to have a strong defense in 2017. He's the team's most talented player, and with a system built around a four-man pass rush, it's critical that the Eagles defensive line gets to the quarterback more frequently this season. Cox must be a big part of it.

His contract can create unrealistic expectations – no defensive tackle reached double-digit sacks last season – but it's reasonable to expect more than 6.5 sacks. The Eagles made changes on their defensive line that could help with the pass rush around Cox. One of the major changes was letting Bennie Logan leave in free agency and acquiring Tim Jernigan from Baltimore. Cox and Logan played next to each for four years and developed a strong rapport. Cox must know how to play off Jernigan, but they both can penetrate from the interior.

At age 26 and entering his sixth NFL season, Cox is clearly in the prime of his career. The franchise has made him a foundation piece, and the defense is supposed to be an ideal fit. That was apparent at the beginning of last season – the Eagles need it to be clear throughout 2017.

On the 53-man roster: Tim Jernigan, Beau Allen

Jernigan and Allen are the top candidates to replace Logan. Both are entering their contract years. Allen is recovering from a pectoral injury that could keep him sidelined into the season, giving Jernigan the edge to start. The Eagles acquired Jernigan from the Ravens in a draft-pick swap, and the former second-round choice has 13 sacks in three seasons while starting 24 games. The 24-year-old is a good athlete who has played in a 3-4 defense throughout his first three years. He must transition to Schwartz's system, but the Eagles are optimistic about how Jernigan will fit. With a strong season, he could earn a multi-year contract that will make him a major piece of the defense moving forward.

Allen, 25, has been a role player with the Eagles. He has one sack and five career starts, and spent the first two years as a space-eating nose tackle in the middle of the Eagles' line. After playing 40 percent of the defensive snaps last year, he seemed the likely candidate to replace Logan before the Eagles acquired Jernigan. At 6-3 and 327 pounds, he gives the Eagles a big, stout body that could continue to be a rotational defensive tackle even if he's not starting. But he first must recover from the injury that will keep him out this spring and summer.

On the 53-man bubble: Destiny Vaeao, Justin Hamilton

After missing out on defensive-tackle targets in the draft last year, the Eagles were high on Vaeao as an undrafted rookie. He earned a spot on the 53-man roster and was active for all 16 games, playing 26 percent of the defensive snaps and totaling two sacks. It was a solid rookie year, and there's reason to be optimistic about his continued development. He's listed on the bubble list only because the Eagles have rookies who will compete for playing time and his roster spot.

Hamilton was signed to a futures contract after the season. He has not yet played in an NFL game after bouncing among three NFL teams. Hamilton might not have any more luck in Philadelphia.

Draft picks: Elijah Qualls

The Eagles used a sixth-round pick on Qualls, who expected to be drafted sooner. Qualls is 6-1 and 321 pounds with relatively short arms, but the former high school running back is quick and was productive in college for Washington. Often needing to occupy blockers, Qualls recorded 7.5 sacks the past two seasons and was first-team all-Pac-12. He'll compete with Vaeao for a roster spot.

Undrafted rookies: Winston Craig, Charles Walker

The Eagles signed two undrafted rookie defensive tackles. Craig went to Richmond, Joe Douglas' alma mater, and was second in the Colonial Athletic Association in sacks. Walker left Oklahoma after four games last year, has a history of concussions, and was diagnosed with depression. His six sacks and 10 tackles for a loss in 2015 show that there is talent the Eagles will try to unearth.