Courtesy of Geoff Burke, USA Today Sports

Evan Mathis departed from the Philadelphia Eagles on not-so-excellent terms, and he still isn’t thrilled about the time he spent there under Chip Kelly.

In an e-mail conversation with Mike Klis of 9News, the Denver Broncos left guard said Kelly did “many things” that proved he wasn’t building or capable of dealing with a championship-worthy team.

“Two of the main issues that concerned me were: 1. A never-evolving, vanilla offense that forced our own defense to play higher than normal play counts. 2. His impatience with certain personality types even when they were blue-chip talents. The Broncos team I was on would have eaten Chip alive. I don’t think he could have handled the plethora of large personalities.”

Mathis’ primary concern definitely showed itself in 2015, soon after Kelly took control of Philadelphia’s personnel.

The Eagles signed DeMarco Murray, the NFL’s best rusher the year before as part of a single-back pro-style system. Murray’s straight-forward running style didn’t mesh with Kelly’s off-tackle preference, which perfectly suited ex-Philly standout LeSean McCoy who was traded to the Buffalo Bills.

However, the bigger problem was Kelly relied on pocket-passing quarterbacks like Nick Foles, Mark Sanchez and Sam Bradford.

According to Ian Rapoport of NFL Media, Tyrod Taylor was interested in signing with Philadelphia last offseason. He was an unknown commodity at that point, so that’s not necessarily as egregious an error as it looks today. Going with Tim Tebow over Taylor, however, remains questionable.

Kelly had opportunities to evolve the offense but didn’t take them. The Eagles became predictable, whether Kelly wants to admit it or not.

And then there’s the reported issues with players like McCoy, DeSean Jackson and Brandon Boykin. Each of them were significant contributors but either traded or allowed to leave in free agency. While some called Kelly a racist, Boykin said he felt Kelly couldn’t relate and was a poor communicator.

Ultimately, the issues led Philadelphia to release Mathis prior to the 2015 season and fire Kelly before the campaign ended. Mathis won a Super Bowl with Denver, and Kelly moved on to the San Francisco 49ers.

If Kelly’s offense doesn’t evolve there, don’t expect to hear Mathis say the 49ers can win a championship.