Still a lot of uncertainty at cornerback

This is what we know about the Eagles' cornerback situation 18 days before the season opener against the Washington Redskins:

If Ronald Darby and Jalen Mills manage to make it to the Sept. 10 starting line without getting hurt, they will be the team's starting corners.

After that, well, everything's still very much up in the air.

[Darby has exactly what the Eagles desperately need]

Patrick Robinson might be the Eagles' season-opening nickel corner or he might be gone.

Ron Brooks might be the nickel corner or he might be gone.

The final two preseason games will decide the immediate futures of Aaron Grymes and C.J. Smith. One or both could make the team. One or both could be gone or start the season on the practice squad.

The only corner beyond Darby and Mills who can breathe easy as far as cutdown day is concerned is rookie Rasul Douglas. But that's largely because of his third-round pedigree. He's a work in progress, and it remains to be seen how much he'll play early on.

"I feel good that when we get to Washington, we're going to have a solid group out there,'' defensive backs coach Cory Undlin said. "But we've still got another two weeks [left in the preseason]. Until we get there, I don't know how it's all going to shake out.''

Robinson's future with the team could hinge on his ability to prove to defensive coordinator Jim Schwartz that he can cut it inside as a slot corner.

Robinson, a seven-year veteran who signed a one-year deal with the Eagles in late March, has spent most of his career playing outside. But he couldn't beat out Mills, and when the team acquired Darby from the Buffalo Bills on Aug. 11, they started giving Robinson reps in the slot.

Given the division the Eagles are in, that third corner spot is vitally important. The Cowboys' Cole Beasley, the Redskins' Jamison Crowder and the Giants' Sterling Shepard are three of the best slot receivers in the league and were thorns in the Eagles' side last season.

Beasley led the Cowboys in receptions (75) and receiving yards (833) last year. He finished 17^th in the league in first-down receptions (51). In two games against the Eagles, he had seven catches, six of them for first downs.

Shepard had 10 catches, including two for touchdowns, and six first downs in two games against the Eagles as a rookie last year. And Crowder averaged 17.8 yards per catch against the Eagles in '16, and scored the Redskins first touchdown on a 16-yard pass from Kirk Cousins in their 27-20 Week 6 win over the Eagles.

Bottom line, neutralizing those three is going to be every bit as critical as stopping Dez Bryant, Odell Beckham Jr. and Terrelle Pryor.

[Archive: Eagles' secondary a primary issue]

"There are some really good slot guys in this division,'' said Mills, who played most of his 661 rookie snaps last year inside. "You've got to get on them, have great feet and great hands, for sure.''

Brooks is a solid inside corner. Did a nice job there last year until suffering a season-ending quad injury in the sixth game of the season. But he's been sidelined much of the summer with a hamstring injury, and there are concerns about his ability to stay healthy.

The appeal to Robinson inside is his speed. For the most part, change-of-direction ability is more important than speed in the slot.

But against Beasley, Shepard and Crowder, it's important to have someone who, as Mills pointed out, can "get on them'' quickly and disrupt their timing with the quarterback and give the pass rush an extra split second.

The Eagles' problems with their pass rush and pass defense really became magnified in four late-November, early-December losses to Seattle, Green Bay, Cincinnati and Washington when opposing quarterbacks started taking short drops and getting the ball out quickly, usually to open slot receivers and/or tight ends.

That's what Schwartz wants to eliminate this season. That's why the possibility of using Robinson in the slot is intriguing to him, assuming he can prove to him that he can play it well.

"Pat's played nickel in the past,'' Undlin said. "It's a great opportunity to put Darby outside. We're not going to put [Darby] in the nickel. And I don't want to move Jalen back there either.

"When Brooks was hurt, it was a good opportunity for Pat to go out there, get some snaps, learn it during the week, and then, if we end up sticking with that, we have some evaluation of him being down there. But we haven't made a decision on any of that.''

Brooks returned this week and took limited snaps during the Eagles' joint workouts with the Dolphins. It remains to be seen whether he'll play Thursday night.

Robinson is expected to get some first-team reps at slot corner against the Dolphins.

He has played inside before in his career, most recently in 2015 with San Diego.

"It's been great,'' he said. "It's been a smooth transition. Things happen a little faster in there, so your eyes have to be right. But so far, I haven't had any problems.''

When you play in the slot, you're responsible for both the run and the pass. You're part linebacker, part cornerback.

"You have to be more aggressive, more hands on, in nickel,'' Robinson said. "You have to have your mind right. You have to know your assignment and be focused.''

If the Eagles end up deciding to use Robinson in the slot, it likely would be mainly on third down and in obvious passing situations. On early downs, Undlin said they probably would just drop safety Malcolm Jenkins down in the slot to defend against the run.

They have used some packages where Jenkins has dropped down and Corey Graham has replaced him at safety.

"There will be situations where we'll want (Jenkins) down there,'' Undlin said. "It gives us another look. We like Malcolm there with that first group where he can be physical. Especially on early downs when they're going to run the ball.''