Chip Kelly stood on the field at Ladd-Peebles Stadium in Mobile, Alabama, back in January 2013 and was peppered with questions about the innovative methods he planned on bringing to the NFL.

Kelly had been hired as the Philadelphia Eagles‘ head coach days earlier and had already begun scouting at the Senior Bowl. But he seemed annoyed by the idea that he was some kind of revolutionary.

“If you weren’t in the room with Amos Alonzo Stagg and Knute Rockne, then you stole it from somebody,” Kelly said often. “We didn’t invent this.”

But the truth is, he did do things differently in Philly:

The Eagles ran a no-huddle program that focused on tempo and efficiency. They hired a former Navy SEALs coordinator to head their sports science department. They focused on nutrition and sleep and physical conditioning.

And while there were plenty of positives — Kelly went 26-21, put together a pair of 10-win seasons and made the playoffs once — the most important pillars of Kelly’s philosophy ultimately failed to yield positive results. And that is why he is no longer the Eagles’ head coach.

Kelly believed in shrinking the playbook on offense. The thinking was that if the players focused on perfecting foundational plays through a high number of reps at practice, they would be able to execute at a high level, regardless of the situation. Yet the Eagles too often seemed incapable of completing the simplest of tasks. They became more predictable, and defensive coordinators adjusted. Despite the innovative practice philosophy, Kelly coached a team that turned the ball over 65 times since the start of the 2014 season, more than any other team in the league.

The sports science program and practice schedule were supposed to help the Eagles peak late in the season. Yet in 2014, the team started out 9-3 before losing three of their last four and missing the playoffs. They have stumbled down the stretch this year, too, getting outscored 78-41 in back-to-back losses to the Arizona Cardinals and Washington Redskins.

Culture was supposed to be greater than scheme. That’s what NFL Films caught Kelly telling a player on the sidelines last summer. However, during Kelly’s first training camp, when wide receiver Riley Cooper was caught on video using a racial slur, he was sent away for just four days before returning. Neither Kelly nor the organization specified how Cooper had spent his time. The next offseason, the Eagles signed him to a contract extension.

The word Kelly constantly harped on was execution. But players are not robots. If they executed perfectly, every coach would look like a genius. When players fail to execute, it ultimately means they are not good enough or the coaches are not doing their jobs.

That’s why after the 2014 season Kelly wrestled full personnel control away from general manager Howie Roseman. Kelly overhauled the roster, trading LeSean McCoy to the Buffalo Bills, acquiring Sam Bradford from the St. Louis Rams and signing DeMarco Murray as a free agent.

Kelly placed an enormous emphasis on measurables. Cornerbacks had to be a certain height. Defensive linemen had to have the proper arm length. Wide receivers had to be a certain size. There’s nothing wrong with having prototypes; that’s common around the NFL. But Kelly showed little flexibility, and eventually his guidelines proved to be too stringent.

His biggest downfall in terms of personnel was a lack of understanding value. It’s easy to forget now, but DeSean Jackson had a career year for Kelly in 2013, catching 82 balls for 1,332 yards and nine touchdowns. He looked like the perfect fit for the new Eagles’ offense, but Jackson and Kelly did not mesh, and the wide receiver was let go without the team getting anything in return.

This past offseason, Kelly tried to sell the McCoy trade as a financial move, yet he proceeded to offer more guaranteed money and a less team-friendly contract to Murray.

When guard Evan Mathis didn’t show up to voluntary OTAs because he wanted a new contract, Kelly released him.

Asked if that set a bad precedent of allowing players to get out of their contracts when they were unhappy, Kelly said, “It’s a bad precedent if guys don’t like their contract. They can sit out, and you can pay them more. You look at it both ways. You have to make that decision.”

But what about the third option of just making them play out their deal?

“That wasn’t an option we wanted to go with,” Kelly said. “If he doesn’t want to be here, he doesn’t have to be here.”

Owner Jeffrey Lurie was paying Kelly $6.5 million per season to field the best possible team and deal with difficult situations. But too often Kelly’s solution was to simply get rid of the players who presented problems. In a vacuum, none of those decisions doomed the Eagles. But with Kelly, the process often left a lot to be desired.

There is the argument that Kelly’s failures rest with his inability to find the right quarterback. He started off with Michael Vick before coaching Nick Foles to a remarkable 2013 season, during which he tossed 27 touchdowns and two interceptions. Kelly drafted Matt Barkley and signed Mark Sanchez, twice. He traded a second-round pick for Bradford this past offseason. Bradford seemed to be improving and said this week he wanted to come back for a second season. But Kelly was never able to find or develop a guy who had the skill set to operate his offense for the long term.

Kelly is probably no more stubborn or arrogant than the other 31 head coaches in the NFL. At times, his offense has dazzled. And he is a bright football mind. There is no questioning how much the game means to him. Bill Belichick and Urban Meyer are among the coaches who have sung his praises.

His methods — the tempo, the practice schedule, the sports science, how he called plays — impacted the league for three years. He is a football lifer, and he will eventually find a new home. At some point, whether it’s this offseason or down the road, he might even get another chance to coach in the NFL.

If and when that happens, though, it will be up to Kelly to examine why his tenure in Philadelphia didn’t work. If he tries to bring the same philosophies to a new coaching stop — harping on execution and hoping for a different outcome with new players — the experiment once again will lead to unsatisfying results.