It can happen.
Some NFL beat writers have been going to great lengths lately to poo-poo the idea of a successful NFL coach going back to college. Well, as you can imagine there are a bunch of NFL guys who've gone back to coach college, though not so many with a legit shot at an NFL position in a short (year-ish) window.
Typically when it happened, it was successful college coach who wasn't very successful in a short NFL stint. There's Saban and Spurrier of course. Also new Nebraska head coach Mike Riley spent three bad years coaching the Chargers in between tenures at Oregon State. Dan Devine, Bill Callahahan, John Mackovic, Butch Davis, Rich Brooks, Gene Stallings, June Jones, Paul Wiggin, Lane Kiffin (giggle), Howard Schnellenberger, Bobby Petrino, Bill Arnsparger, and Lou Holtz all coached one to four years in the NFL without getting to the playoffs. Dan Henning, Forrest Gregg, and Dennis Erickson are three examples of established pro dudes who exhausted their NFL opportunities before accepting demotional collegiate positions.
Between 8 and 10 of the 30 NFL head coaches I could find who went back to college appeared to have some competing pro prospects. They were:
|Though just 60 when the took the job, Walsh, who'd walked away on top of the NFL at 56, wasn't expected to be a long-term answer for Stanford. [Gerry Gropp]|
NFL Record: 92-51-1 with 49ers, 1979-'88. Won Superbowls, established a dynasty, staffed a generation of NFL jobs with his assistants. All-around badass.
College Record after NFL: 17-17-1 at Stanford, 1992-'94
Walsh is the go-to comparison because he's certainly the greatest NFL coach to ever return to the college ranks, but he's also not very instructive, since he walked away from coaching for three years before surprisingly returning to college.
After winning Super Bowl 23 Walsh voluntarily retired, citing burnout, and went to work in broadcasting. Everyone expected he would continue to do so. But in 1992 Stanford, where he'd developed the West Coast offense and been head coach for two years in the late '70s, begged him to come back (he turned 61 that season). There's a book about the return, wherein Walsh says he didn't like broadcasting and was getting an itch.
Certainly ANY NFL team would have taken him. And the Stanford he returned to wasn't a Michigan, but they had gone 8-4 in '91 and returned most of that team. In his first year back, Stanford was 10-3 and shared a piece of the conference championship (but didn't get the Rose Bowl nod, having been creamed by Washington). They regressed back to near the bottom of the conference in 1993 and 1994, losing a lot of close games to top 10 teams in that period, and Walsh re-retired. He lived out his days around the Stanford program, teaching classes and writing books.
[Jump for guys who aren't in the conversation as greatest coach in history]