PHILADELPHIA (973espn.com) - Jim Schwartz and Cory Undlin have plenty of bodies to work with in the defensive backfield for the Philadelphia Eagles but many of the proven contributors remain a question mark as they continue to work their way back from injuries.

Three of the projected starters - cornerbacks Ronald Darby (ACL) and Jalen Mills (foot) as well as safety Rodney McLeod (ACL/MCL) -- missed spring work as they continued to rehab from surgeries.

THE RETURNS

Interestingly McLeod and Darby, who are both coming off torn ACLs, seemed a little closer than Mills, who suffered a bit of a mysterious foot injury that seemed to go backward at times during the healing and rehab process. All are expected to be ready to go for the season opener in September but it will be interesting to see if any are ready for the start of training camp next week.

If there is any concern at all the Eagles will likely play it safe because there is no real need to ramp up veteran players. Meanwhile, part of the silver lining to the injuries to Darby and Mills last season was getting experience and playing time for young corners like Avonte Maddox, Rasul Douglas, Sidney Jones and Cre'Von LeBlanc.

SLOT STAR?

Of that group Maddox, despite his size limitations, showed the most promise and that carried over to the spring where he was the starter at left corner in the base defense with Mills out before kicking inside to the slot in the nickel, which is really the default defense in the modern NFL. Jones would then take over outside the numbers when Maddox kicked inside.

THE FIT

The biggest question at CB is how the Eagles handle that left corner position because the talented Darby, after re-signing a one-year prove-it deal in the offseason, is penciled in on the right side and Maddox will ultimately handle the slot duties. The status quo on the left side is Mills, who is entering the final year of his rookie deal, but he could be everything from three-down player to a subpackage option or a backup. Both Maddox and Jones have better pedigrees and could push the LSU product into a subpackage role or even off the field bur remember Mills remains a Schwartz favorite especially in the red zone.

Jones, on the other hand, needs to step it up and show he can handle the rigors of the professional level.

"It was a tough season for him, but he did experience some success," Schwartz said of the 2018 second-round pick. "He saw some tough times. Persevered through it. Finished the year healthy even though he wasn't really back on the field for us. It's an important off-season, important training camp for him."

Douglas, a fellow third-year corner, has plenty of size and impressive ball skills and is expected to be Darby's backup on the right side. If the Eagles decide to keep six corners, a good idea in the modern NFL, LeBlanc proved he can be a capable slot corner as well when pushed into action last season.

THE DEPTH

The depth at the position even has some wondering if Howie Roseman might try to spin one off to address a need at another position. In that case Josh Hawkins and Jeremian McKinnon, who both saw plenty of second-team reps in the spring, would enter the conversation.

"Some of the younger guys we want to try to settle in at one position and let them compete there," Schwartz said of his crowded CB room. "But once you're in the mix of making our roster, you have to have some versatility: play inside, play outside, play safety, play corner. All those things help you not only make the roster but help us over the course of the season."

VETERAN EXPERIENCE

At safety the big move was bringing in veteran Andrew Sendejo as the third safety to replace Corey Graham. Sendejo has extensive starting experience on a top-five defense in Minnesota and his role was to play single-high opposite All-Pro Harrison Smith, exactly what Schwartz is seeking for his big-nickel package when Malcolm Jenkins becomes the most important chess piece on the defense.

MALCOLM IN THE MIDDLE

Jenkins, the quarterback of the back end, missed voluntary work this spring while jockeying for a new contract but did show up for mandatory minicamp and doesn't plan any type of holdout after clearing the air with owner Jeffrey Lurie.

“As a player, I feel I’ve outplayed that contract,” Jenkins said back in June when discussing his current deal which has him on the books for an $8.1M base salary in 2019 and a cap hit of nearly $11.4M. The guaranteed money has dwindled, though, and includes just $1.75M in bonuses for 2020, the final year of the deal.

The safety position as a whole has spiked from a salary perspective with lesser players than Jenkins like Landon Collins, Tyrann Mathieu, Lemarcus Joyner and Adrian Amos cashing in due to timing and circumstance.

"When you’re under contract, you can’t be out to be the highest paid out there, nor do I want to be, but you want to be within the ballpark of what your value is," Jenkins explained.

While Fletcher Cox is widely regarded as the best Eagles defender, Jenkins, 31, might be the most valuable because of his ability to move all over the back end of Schwartz's unit.

“For me, I think they understand the value that I bring,” said Jenkins. “I feel respected, which I think is the biggest part. As a player, you want to make sure that you are valued and that you feel respected. There is a business side of it and there are things involved there."

Nothing has been adjusted with the contract yet but Jenkins was at mandatory work lining up with the first team at safety next to Sendejo, who was filling in for rehabbing McLeod.

“Those things are ongoing," Jenkins said of a potential restructure. "For me, I hire an agent to have those conversations. Mr. [Jeffrey] Lurie hires the GM to handle those conversations. So, I’m here. I’m focused solely on making sure that the product on the field is the standard that I want.

"... At the end of the day, I think everybody wants to win. I love being an Eagle, I love being here, I love this team, this locker room and I want to be a part of it, and that’s why I’m here."

McLeod's return will be interesting and he's on a contract year so he has plenty of incentive. Tre Sullivan, meanwhile, earned more trust as the season wore on in 2018 and figures to be the leader in the clubhouse for the fourth safety although there is significant competition including the returning Blake Countess, Deiondre' Hall, who both excel on special teams, and Godwin Igwebuike.

Chris Maragos' retirement earlier this week in advance of his third surgery for a PCL injury first suffered back in October of 2017 is also a stark reminder that you can't just pencil in players returning from injury.

DEPTH CHART:

LC1 - Jalen Mills - Jim Schwartz favorite will try to hold off the competition.

RC1 - Ronald Darby - The Eagles best corner tries to shake off the injury tag after a torn ACL derailed 2018.

SS1 - Malcolm Jenkins - The most important and versatile player on the defense wants a new deal.

FS1 - Rodney McLeod - McLeod returns to center field after a serious knee injury.

SC1 - Avonte Maddox - Maddox will be on the field. The question is how much?

LC2 - Sidney Jones - Jones needs to get stronger and more physical.

RC2 - Rasul Douglas - Zone corner with great ball skills.

S3 - Andrew Sendejo - Veteran with a ton of experience which is exactly what Schwartz wants in the third safety role.

ON THE BUBBLE:

SC2 - Cre'Von LeBlanc - Eagles got him off the street in November and he held up well.

S4 - Tre Sullivan - Slowly earned more trust as 2018 wore on but faces tougher hurdles this season.

S5 - Blake Countess - Good special teams player who has CB in his background, something Jim Schwartz likes.

S6 - Deiondre' Hall - Hall is facing a tough numbers game this year.

LONGSHOTS:

S7 - Godwin Igwebuike - Father Donald was the former Tampa Bay kicker.

CB8 - Josh Hawkins - Could find himself in the mix if Howie Roseman decides to move a CB.

CB7 - Jeremiah McKinnon  - Got a lot of valuable reps in the spring.

CB8 - Jay Liggins - UDRFA's best hope is the practice squad.

S7 - Trae Elston - Late-signing when the Eagles needed a bosy at S in the spring.

POSITION GRADE: 6.0 [There are plenty of bodies but also needs to fight the right fits and for the younger players to live up to projections.]

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen

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-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen