PHILADELPHIA (973espn.com) - The start of the "legal tampering" period in the NFL began with promising news when it came to Patrick Robinson.

With the start of the new league year rapidly approaching, however, things took a turn and the Eagles lost to their star slot cornerback to his NFL roots.

The former first-round pick is returning to the city where it all started for him, New Orleans.

The Saints agreed with Robinson on a four-year deal worth $20 million with half of that guaranteed and the veteran easily shapes up as the Eagles biggest loss in the opening days of free agency.

Playing on a one-year, prove-it deal last season, Robinson turned out to be one of the best slot cornerbacks in football, a position that is no longer a sub-package one as evidenced by the fact the veteran played in 68.9 percent of Philadelphia's defensive snaps (853 total).

The value was incredible as Robinson finished last season with 47 tackles and four interceptions while his pick-six in the NFC Championship Game against Minnesota completely changed momentum in that one sending Philadelphia on to Super Bowl LII,  grading out as the sixth-best cornerback in the NFL by ProFootballFocus.com.

And the Eagles got all of that for $775,000.

From a production standpoint, it was inconceivable that Philadelphia wouldn't want Robinson back and they were working on an extension but once other teams got to talk with the 30-year-old, the numbers simply got too large.

The assumption that the Eagles have plenty of depth at the CB position is both true a bit specious.

The starters on the outside of the defense -- Jalen Mills and Ronald Darby -- as well as talented second-year players Sidney Jones and Rasul Douglas, and the recently acquired Daryl Worley all project better on the outside vs. navigating the traffic in the slot with perhaps only Mills possessing the kind of skill set to move inside, an entirely different position requiring short-area quickness as well as the savviness to handle option routes run by disciplined receivers.

Versatile safety Malcolm Jenkins has proven he can handle slot work in the past but Jim Schwartz has never wanted that to be a full-time role for his star safety.

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