PHILADELPHIA (CBS) -- Fletcher Cox's time as an Eagle has come to an end ... maybe. The Birds have released the star defensive tackle with a post-June 1 designation.

NFL Network's Mike Garofolo reports Cox was due $18 million in fully guaranteed money at 4 p.m.

The 31-year-old's time in midnight green may not be over just yet though.

ESPN's Adam Schefter reports the Eagles are working to sign Cox to a reworked deal. NFL Network reported on Thursday night that the Eagles and Cox are "making progress on a deal."

Cox was selected 12th overall by the Eagles back in 2012 and has been a mainstay on the defense over the last decade.

Cox, a six-time Pro Bowler and 2018 All-Pro, is free to sign with another team.