Evan Mathis knows what a Super Bowl-winner looks like. He didn't join the Denver Broncos until late in the 2015 NFL season and even after he did he missed plenty of snaps due to injury, but Mathis spent enough time with the NFL's Colorado-based franchise to learn just what it takes to win a Lombardi Trophy. One of the biggest takeaways for Mathis from the experience - whatever Chip Kelly had been building with the Philadelphia Eagles, wasn't a Super Bowl contender.

"There were many things that Chip had done that showed me he wasn't building a championship team," Mathis wrote in an email to Mike Klis of Denver 9News. "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."

San Francisco 49ers fans, only a few short weeks into Kelly's tenure, won't be happy to read Mathis' words. But it's not the first time either of these complaints has been levied against Kelly. He came into the NFL after a stellar run at Oregon wherein he had complete control of a roster full of college players. After finding success and a playoff berth his first season in Philly, Kelly's grip on the team and the organization seemed to tighten. He jettisoned big-name, big-money players like LeSean McCoy and DeSean Jackson, ostensibly for "football reasons," but more likely because they didn't fall into line quick enough.

The result of Kelly's ascension to football czar last offseason wasn't a stronger, more cohesive team - it was one that made more mistakes and seemed unable to break itself of any issues that would arise.

In the end, Kelly's breakneck offensive tempo wasn't enough to offset the fact that opposing defenses often knew what plays were coming, causing an overabundance of three-and-outs that eventually took its toll on a defense more talented than their results the last few seasons would attest.

Kelly was ousted by Eagles owner Jeffrey Lurie with one game left in the 2015 season, at the same time as Mathis was working to get his ankle healthy for what was expected to be - and ultimately was - a deep playoff run with the Broncos.

Now in San Francisco, Kelly no longer has personnel control and faces an offseason of intense scrutiny and uncertainty (boy, that Niners roster needs some work), while Mathis, 34, is preparing for season two in Denver as the Broncos (set for a bevy of changes of their own) ready to defend their NFL crown.

In the end, what Mathis wrote wasn't surprising, but it likely is interesting for Eagles fans who still feel the sting of all of last offseason's optimism gone to waste.

Here's to hoping Mathis won't have to send Broncos head coach Gary Kubiak any Engelbert Humperdink videos any time soon.