Chip Kelly and Rex Ryan were geniuses at different times for the same amount of time: two years. That's how long each of them had atop that pedestal before the rest of the NFL knocked them off. If you're a head coach and want to be a genius for more than two years, you'd better have Joe Montana or Tom Brady as your quarterback. Otherwise, there will be a reckoning, and it will be humbling.

Kelly's reckoning, of course, began in the final four weeks of last season, his second with the Eagles, and has continued through the first 12 weeks of this one. His up-tempo, simplified-playbook approach to offense doesn't catch opponents off guard as often as it once did, and his reliance on a rigorous sports science program has at times inspired eye rolls from at least some of his players. After going 10-6 twice under him, the Eagles are 5-7 this season ahead of Sunday's game against Ryan's Buffalo Bills (6-6), and Kelly is facing much more skepticism about whether his methods can and will succeed over the long term than he did when he was a new, fresh thing in the league.

Ryan wasn't quite as new when he became a head coach in 2009, with the New York Jets. He had been a recognizable assistant coach and coordinator with the Baltimore Ravens, with an even more-recognizable father. But he certainly was fresh. He was brash and outspoken and open and funny in ways that punctured the stuffy, secretive, self-important personae that too many NFL head coaches maintain. He ran his locker room as if it were a graduate-level phys-ed class, relying on the organic mixture of machismo and arrogance and self-discipline to control his team's culture.

That style - combined with a top-notch defense - worked for Ryan's first two years in New York, when the Jets twice reached the AFC championship game. In Ryan's third season, though, the threads holding together his high net started to fray. There was locker-room tension and infighting. There was Ryan's relative disinterest and ignorance when it came to his team's offensive strategy and personnel. There was his belief that, to improve, all the Jets needed was more Rex Ryan.

"I tried to lay back and maybe be more of a 'head coach' than being true to myself," he said in January 2012, just when his tenure with the Jets was beginning its downturn. "I need to be in the locker room. I need to be around more, be involved more right there in the meeting rooms and everything else, and that's what I plan on doing. I got away from doing that, thinking maybe a head coach was supposed to act a little differently, and it hurt me. I need to be myself and stay true to that."

The Jets went 18-30 over Ryan's final three seasons before they fired him, and it appears that in his first season in Buffalo, Ryan hasn't changed much. He told reporters the other day that he doesn't care much for offenses that have their quarterbacks looking to the sidelines for plays - a comment that would seem a veiled criticism of Kelly and his system. And defensive back Jaylen Watkins, whom the Eagles drafted last year and who spent this season on the Bills' practice squad before the Eagles re-signed him last month, said that Ryan's free hand in managing his players still offers a stark contrast to Kelly.

"Coming from here, you're going to what people call 'the real NFL,' " Watkins said. "We run a lot of different things here. But over there, the guys did the same things that guys do here - on their own, though. Rex does have a lot of good guys there. I never saw anyone there taking advantage of his lenience. Some of those guys could come over here, and it wouldn't be a problem. They just want to be better players."

So much for being humbled. So much for reevaluating his approach. Rex Ryan got a second chance in Buffalo, and he seems to be the same coach he was in New York. New city. New players. Maybe it works for him this time. Maybe he can be a genius again. It's yet to be seen whether Chip Kelly can rediscover that magic, that blessed place high on that pedestal, without having to leave Philadelphia first.

@MikeSielski