Asomugha and the Eagles spent recent days seeing if a restructured deal made sense for each side.
But after discussions that started at the NFL scouting combine in Indianapolis and ended Tuesday, neither could bridge their differences.
"Coach [Chip] Kelly and I each had a chance to speak with Nnamdi earlier and he took the news with a lot of class," general manager Howie Roseman said in a statement on the team's website. "We expected nothing less than that from him. He has been a true pro on and off the field for this organization and our community and we wish him all the best as he continues his NFL career. We spoke to his representatives at the combine about his future status with the team and wanted to take time to analyze and make a decision. In the end, Coach and I both felt we needed to move in a different direction at the cornerback position for 2013 and beyond."
Asomugha was scheduled to make $15 million in 2013, $4 million guaranteed.
A three-time Pro Bowler with the Raiders from 2003-10, Asomugha has been a major disappointment with the Eagles since signing a five-year, $60 million contract in 2011.
Now, after spending recent seasons with Oakland and Philadelphia and being the most sought-after free agent in the 2011 offseason, the 31-year-old Asomugha wants to find a winning team and will hit the market in search of one.
Asomugha's agent, Ben Dogra, could not be reached for comment on Asomugha's future.