One of those instances came in, of all places, a hotel ballroom in Toronto in the 1990s. Brian Billick, who would go on to become a Super Bowl-winning head coach with the Baltimore Ravens in 2001, was attending a football clinic, and at one point he noticed an energetic—almost frantic—heavyset man talking football. It was a young Rex Ryan.
"It was truly a remarkable thing to see," Billick, now an analyst for the NFL Network, recounted to B/R. "He was clinic-ing his butt off."
Ryan was spouting an intense blitzkrieg of football philosophies and strategies as other coaches, including Billick, looked on. Billick was so impressed he thought: If I ever get a chance to hire him, I'm going to do it.
Billick told Ryan of his plan and later kept true to his word. When Billick was named head coach of the Ravens in 1999, he hired Ryan as his defensive line coach.
It was a good fit. Ryan already had a genetic predisposition to defensive prowess, thanks to being the son of perhaps the greatest defensive football mind who ever lived, Buddy Ryan. As a defensive assistant with the Ravens, Rex honed his already formidable levels of energy and skill. He coached with smart defensive men in Baltimore such as Marvin Lewis, Jack Del Rio and Mike Nolan. In time, Ryan himself became one of the smartest defensive tacticians of his generation.
"He is truly a brilliant football mind," Billick said. "I can say he is one of the smartest people I've ever been around."
That is one part of the Ryan legacy. There is another—filled with a haze of losing seasons, bar fights and busted guarantees—and it is fueling talk that his coaching career, along with that of his brother, Rob, may be at an end.
The obit goes like a little like this: Here lies the career of Rex Ryan, a brilliant defensive alchemist whose achievements couldn't match his big mouth.
The brilliant man Billick noticed at the coaching clinic developed into one of the true defensive geniuses the league has ever seen but couldn't get out of his own way as a head coach. At some point, Rex and Rob crossed a line from being talented coaches (especially Rex) into showmen, and each became more concerned about the latter than the former.
Billick, the man who gave Rex his first NFL job and mentored both Ryan brothers, is more charitable.
"He did a lot of great things as a head coach," Billick said of Rex. "He won some big games. He won a lot of games. Of course, as a head coach, the winning and losing stops with you. But there are other circumstances that are part of evaluating a coach."
To be fair, Rex was not served well by front offices at times. He managed to make two AFC title-game appearances with the Jets, but in later years with that team and afterward with the Bills, he wasn't given the most talented of rosters, to put things kindly.
Despite putting together a career 61-66 record, Rex was able to carve out an eight-year career as a head coach, something his brother was unable to do, partly because of the differences between the two.
"Rex was outspoken, smart, spoke honestly, told you what he thought," Billick said. "But Rex knew how to play the game. He knew that—right or wrong, whether you agree or not—that to some owners, physical appearance mattered."
Ryan underwent lap band surgery to at one point go from 348 pounds to 218. Rob was different. He kept his hair disheveled and long, and his potbelly stayed. Rob didn't care what people thought of his physical appearance.
"I admired Rob's view of things in some ways," Billick said. "He said, 'I'm not changing how I look. Teams can take me how I am or don't. I don't care.'"
Beyond the trappings of appearance and comportment, the biggest criticism I've heard of Rex (and to some degree his brother) was how he almost overcompensated in being a player's coach. To some of the assistant coaches with whom I talked, including several who competed against Ryan, his uber-closeness to his players was considered maybe his greatest weakness. They contend that the necessary line of demarcation between coach and player was lost, and the result was, sometimes, a lack of discipline from the players.
For now, those worries are a thing of the past. Ryan is now an analyst for ESPN and will appear on the network's Sunday football show. He will be, as he often is, weapons-grade charming. It's the same personality that often got Ryan in the door of a general manager's or owner's office. And it's possible that it could again.
But with a losing track record and a handful of ultimately failed stints on his resume, his career on an NFL sideline may well be over.
That may not be bad for TV viewers, but it likely won't help him change his legacy: a smart, talented coach who failed to back up his big promises.
Mike Freeman covers the NFL for Bleacher Report. Follow him on Twitter @mikefreemanNFL.