Two players added as veteran free agents and another retained. One young prospect on the mend after missing his rookie season. A second-year player who showed signs of excellence in year one. What, exactly, is the picture for the Eagles at the cornerback positions?

It seems to be about adding as many good players as possible, hoping that some of them take the next step in this new defensive scheme and that the level of competition - players pushing players - results in an elevated position, top to bottom.

Nolan Carroll signed his contract on Friday and talked about his comeback from an ugly injury suffered in that awful Thanksgiving Day loss in Detroit. A starter before he went down, Carroll knows he isn't guaranteed anything, not with Eric Rowe stepping in as a rookie and showing so many good things down the stretch, not with Leodis McKelvin and Ron Brooks signed as unrestricted free agents, not with promising JaCorey Shepherd on the mend after missing his first NFL season following a knee injury suffered in Training Camp and second-year man Denzel Rice eager to earn some playing time after making the 53-man roster in 2015.

Why bring back Carroll with such a crowded group?

"The more competition you have, especially at that position is what you want," Howie Roseman said. "You talk about the receivers in this league, how many talented groups of receivers there are, especially in the NFC East ... bringing Nolan back, a guy who has experience, who has played at a high level for us, we're really excited it was able to work out."

Philadelphia's defense of 2016 has already undergone plenty of changes from the one that struggled so much in the second half of 2015. The front is different, with Eagles employing a four-man look in its base defense, with three linebackers on the field instead of four. The ends will line up out wide, outside the tackle box, to give them space on their get-off and give them a better angle to the quarterback. The front seven will play "attacking" defense, getting to the football. The personnel turnover has been extensive, with the two new cornerbacks, a new safety (Rodney McLeod) and a new linebacker (Nigel Bradham). 

There are a lot of questions about how it's all going to come together for coordinator Jim Schwartz, who has had a lifetime of success running defenses and harassing quarterbacks and forcing turnovers and keeping the points-against total down.

At cornerback, the Eagles are certainly going to have depth. Jaylen Watkins, not mentioned above, played a combined 80 snaps in losses to Arizona and Washington before a shin injury KO'd him from the finale at New York. A newly signed player named Aaron Grymes was an all-star cornerback in the CFL last season. Randall Evans was a sixth-round draft pick last May and he spent the vast majority of his first season in the league on the practice squad, so he's ready to take his next step up the ladder.

There are no throwaways at cornerback on this roster, and there could be more to come. Who's to say the Eagles won't use a high draft pick on a cornerback in April? Who is, after all, a shutdown corner here? Cory Undlin remains the coach in charge of the cornerbacks, and he helped Rowe make great strides last season. Is Rowe capable of becoming an elite cornerback? He certainly improved a huge amount in 2015. Rowe's technique was so much more precise after a clunky summer and preseason and the Eagles, who were so high on him in the draft, want to keep him on the island to see how far he can develop.

McKelvin has had some fine years in the NFL and he looks to rekindle his career. The Eagles had him rated highly among the available corners in free agency, and his ball skills relate well to Schwartz's aggressive approach. Brooks can play outside or in the slot. Carroll worked so hard in the offseason last year and earned a starting job and played well in the first half of 2015 before his injury. Shepherd was going to be given every chance to earn the nickel cornerback job before tearing his ACL and losing his season before it really started. 

There is strength in numbers at cornerback, and there is also the need for two or three or four of the players to separate in camp and in the preseason. The Eagles have it tough in the NFC East and non-division games against Atlanta and Green Bay and Pittsburgh and Cincinnati won't be a picnic, either. 

Carroll's return puts a nice cherry on top of the defensive backfield makeover, but there is always more work to be done. You can never have enough cornerbacks the way offenses spread the field in the NFL these days and take advantage of matchups. The Eagles want depth, as much as possible, in their coverage. They want their cornerback room to develop, expand and challenge on every play. Carroll is part of the picture here, one that is still developing and subject to change.