PHILADELPHIA (973espn.com) - Maybe the biggest question mark for a very deep Eagles team during this summer is finding the right fit to replace Patrick Robinson, the veteran slot cornerback who put together a banner year in 2017 as Philadelphia made its run toward a Super Bowl LII championship.

Robinson parlayed his success into a big-money deal with New Orleans in free agency and now Jim Schwartz is trying to figure out how to replicate the success his defense enjoyed last season without a savvy veteran option in the slot.

Through the first six practices of training camp the talented Sidney Jones and the speedy De'Vante Bausby took turns handing the position with the first team defense while Day No. 7 saw starting outside corner Jalen Mills kick inside with Jones replacing him on the outside opposite Ronald Darby, which remains the odds-on favorite to be the protocol come Week 1 against Atlanta with its former MVP quarterback Matt Ryan and impressive receiving corps featuring Julio Jones, Mohamed Sanu, and rookie first-round pick Calvin Ridley.

On Friday, during a scaled-down 10/10/10 session, Sidney Jones was back at the position.

As a whole Schwartz has downplayed the intricacies on the position, which is typically a more complicated one than outside corner because of all the traffic a slot CB has to work through.

Robinson understands the pro game and still possessed outstanding short-area quickness despite reaching the demarcation line of 30. In short, everything you could ask for when it comes to the skill set of a top-tier nickel back.

Most have simply written off the loss because of the presence of the talented Jones, a second-year player who essentially redshirted his rookie season after suffering a torn Achilles at the University of Washington's pro day. Had the injury never occurred Jones was on his way to being a top-15 selection in the 2017 draft.

If playing NFL defense was arithmetic the trio of Mills, Darby and Jones is better from a skill standpoint than Mills, Darby, and Robinson so what's the big deal?

It's about fit and understanding Jones is walking into a world of calculus, not two plus two.

"It's a difficult position to play if you've never played it," Eagles Pro Bowl safety Malcolm Jenkins told 973espn.com. "In the slot, you got to know where your help is. You got to know the ins and outs of the defense. It's like playing linebacker so there is a lot of rules. A lot of moving parts, run fits, watch the guard pulling and all that kind of stuff."

Jenkins, the most versatile Eagles player knows all about playing and excelling in the slot because he's been the team's emergency option at the position since the Chip Kelly days.

"I always get jealous because I don't get any reps at the slot during camp because we are evaluating," Jenkins said. "I probably won't get any until we get close to opening Week 1 but we'll see. Hopefully, for us, it will be a good problem to have if one of these one guys emerges as a strong point in the slot. Patrick Robinson played well for us last year which kept me out of the slot. Selfishly I wanted to be there but it made us so much better as a defense to have me move around to different places."

Schwartz understands better than anyone that his unit is best when Jenkins is moved all over the chess board but to do that he needs two other pieces to emerge: the Robinson role as well as a competent third safety, something another veteran, Corey Graham, was able to provide last season.

Now the theme is youth as none of the Eagles' CBs have extensive experience in the slot and Tre Sullivan, the projected No. 3 safety, has no real resume at this level.

Mike Zimmer, the Minnesota head coach who is often called the cornerback whisperer around the NFL because of his success developing players at the position, talked about why the slot cornerback position is such a difficult transition to make from college to the pro ranks earlier this week.

"It’s not nearly as complicated [in college], number one," Zimmer explained. "Number two, all the different concepts that they have to go against, man within a zone, zones. If it’s just man-to-man, it’s not that much different, but if it’s some of the zones they might have to carry the vertical and then see another guy coming into the zone and pull off the vertical. He might have to carry number two on the vertical or pass a guy off, there’s a lot to it and there is a lot more room in there as well. The guy on the outside, he’s really only covering maybe half of a field. The guy in the slot, he’s got to cover everywhere."

Schwartz has downplayed the lack of experience he has to work with at the spot for good reason.

What else can he do? Circumstance has already dictated he will be using someone with little experience at the position no matter who wins the competition.

"They have challenges just like everybody else," Schwartz said when asked about a young player handling the inside work. "If we had positions that we didn't feel that rookies or inexperienced players could play, we'd have a lot of positions open on the field. So, everybody's got challenges, whether you're a defensive tackle, whether you're a safety or a nickel. Their job is to do their job on the field."

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