The firing and replacement of NFL head coaches has ended with seven slots filled. Three of them (Jim Caldwell, Lovie Smith, Ken Whisenhunt) led teams in the past and four (Jay Gruden, Mike Pettine, Bill O'Brien, Mike Zimmer) move up from assistant coaching-coordinator positions with O'Brien adding the last two seasons as head coach at the collegiate level for Penn State.
While most fans, no doubt, have feelings about whether their team's hiring shines or stinks, the truth is, it isn't much different from draws from a lottery hopper or beauty contest. Data analytics have invaded most every aspect of sports, but this is one area where the numbers don't reveal much other than noise. In the world data miners, I don't doubt that a persistent digger out there may discover some systematic signals of success, but they are very subtle.
Sure, if a college team could hire Alabama's Nick Saban, their chances of success are not random. At the pro ranks, teams seldom get a shot at someone with a long, proven track record. Kansas City's hiring of Andy Reed in 2013 is one of the few examples. The choice between a coach with a modest prior winning percentage and a coordinator with no head coaching experience differs little from a coin flip. The same holds when pulling a successful coach up from the college ranks. For nearly every Jim Harbaugh there is a Steve Spurrier or Greg Schiano.
Prior NFL head coaching experience would seem to be useful indicator. As a friend of mine suggested, a head coach must wear many hats, pointing toward the existence of a learning curve. I suspect that it true, but no such pattern jumps out of the data. If it's in there, it's subject to important caveats and swamped by other influences.
Coaching connections seem to be a common indicator used by general managers. If someone coached under Bill Walsh in the 1980s or Bill Belichick in the 2000s, they were more likely to land jobs. In all sports, general managers and owners lean on coaching pedigree.. In the NFL data, at least, they don't help predict success very obviously. Great coaches spawn about as many dregs as stars.
About the most that can be said is that teams might avoid extremely bad choices by selecting someone like Lovie Smith, who had a solid record at Chicago, but high-end success is not guaranteed. Coaches such as Jimmy Johnson slid backwards in their second stint. On the other side, some coaches with modest to decent records in their first attempts, such as Belichick or Pete Carroll, performed much better in their second chance. Maybe that's learning or maybe it's the luck of a hall-of-fame quaterback like Tom Brady emerging out of a late round, shot-in-the-dark draft pick. The bottom line for fans is that whether they are happy or upset by your team's coaching choice, only time will tell.