Dockett has played his entire 11-year career with the Cardinals, totaling 459 tackles and 40 1/2 sacks. He missed the entire 2014 season after tearing his ACL in the preseason.
Dockett was entering the final year of his contract and saves Arizona $6.8 million in cap space. He also may return to the team wit ha pay cut.
"We have been very clear about our feelings for Darnell and our desire to have him back," Cardinals general manager Steve Keim said of the announcement.
Dockett reportedly failed a physical, leading to his release.