Mathis, 33, was unhappy with the five-year, $25 million contract he signed in 2012 and has skipped all of the Eagles' offseason activities, which were voluntary. The Eagles were scheduled to have three days of mandatory training next week. Mathis could have been fined if he failed to report for those workouts.
Last year, the Eagles gave Mathis and agent Drew Rosenhaus permission to find another team willing to trade for Mathis' services. Mathis received the same permission this year.
The team hasn't yet announced the move, which was confirmed by sources to ESPN, but Mathis tweeted a farewell to Philadelphia shortly after the news broke.
Thanks for the memories Philly.— Evan Mathis (@EvanMathis69) June 11, 2015
Mathis' release was earlier reported by NFL Network.
"Evan's been available to trade for two years now and we've never had an offer for him," Kelly said during the NFL draft. "That's through his agent and him. They've asked if he could renegotiate a contract and see what he could get and we've obliged him with that, but we've never had an offer."
Mathis was scheduled to make $5.5 million in 2015 and $6 million in 2016.
Now Mathis will have to find another job. It will be difficult to find a better contract as teams have their rosters pretty much set and little room under the salary cap to work with.
Meanwhile, the Eagles will have to replace a two-time Pro Bowl guard who regularly ranks at the top of Pro Football Focus' annual assessment of NFL offensive linemen. Mathis was PFF's top-rated guard from 2011 through 2013. He was second last season, playing only nine games because of a sprained left knee.
According to ESPN Stats & Information, Mathis led all Eagles offensive players with 3,675 snaps in the past four seasons. Right guard Todd Herremans (3,139) and running back LeSean McCoy (3,079), third and fourth respectively in snaps played during that span, also are no longer on the team.
Although Mathis was kept to just nine games this past season, he had started at least 15 in three of the previous four years.
After playing for three teams in six seasons, Mathis signed with the Eagles in 2011. Playing alongside left tackle Jason Peters, Mathis found a home. Mathis went to the Pro Bowl after the 2013 and 2014 seasons.
The Eagles released Herremans in March. Herremans signed a one-year deal with the Indianapolis Colts.
At the time, Kelly said that veteran Allen Barbre would slide into Herremans' spot. During recent OTA practices, Barbre was playing left guard. That led to speculation that Kelly didn't expect Mathis back.
Barbre, who will turn 31 on June 22, started the season opener at right tackle last year. He left the game with a high ankle injury that forced him to go on injured reserve and miss the rest of the season. Barbre has started a total of eight NFL games in his career.
At right guard, Matt Tobin is the likely replacement for Herremans. Andrew Gardner and Dennis Kelly could also be in contention for the job. Tobin, who made the Eagles' roster as an undrafted free agent in 2013, started seven games at guard last season.