John Fox went from very employed to not especially employed in a matter of, oh, about 36 hours. The first rumblings I heard about Fox possibly being fired came out Sunday morning, when Jay Glazer reported that the Broncos were considering moving on from Fox if they lost to the Colts that afternoon. When the Broncos lost 24-13 in an uncharacteristically meek performance, the vultures circled. Postgame reports suggested the Broncos had never discussed firing Fox before Sunday’s loss, but after apparently discussing it for the first time Monday, they liked the idea enough to follow through.

Fox and the Broncos “mutually parted ways” Monday afternoon, which is the NFL’s spin on conscious uncoupling. Maybe Fox just happened to decide at the same time as the Broncos did that he would rather not be paid to be their head coach anymore. It seems more logical to treat that as a firing, and in that context, I have to admit it’s a pretty bizarre one. When Jim Harbaugh was fired/mutually parted ways with San Francisco, I mentioned that successful coaches like Harbaugh almost never leave teams this quickly. Fox is an even better example.

There’s a possibility that, in terms of winning percentage, Fox might be the most successful head coach since the AFL-NFL merger to get fired. I went through the coaching history at Pro-Football-Reference.com and tried to identify coaches who were similar to Fox, guys who were wildly successful in a brief stretch before leaving. Virtually all were coaches who retired or left of their own accord. Among post-merger coaches who spent at least 40 games with their organization, Fox has one of the best win-loss records of all time:

Name Team Began Ended Yrs W L T Win% Why Left? George Seifert 49ers 1989 1996 8 98 30 0 76.6% resigned Tony Dungy Colts 2002 2008 7 85 27 0 75.9% retired John Madden Raiders 1969 1978 10 103 32 7 75.0% retired John Fox Broncos 2011 2014 4 46 18 0 71.9% “mutually parted ways” Blanton Collier Browns 1963 1970 8 76 34 2 68.8% retired Jim Harbaugh 49ers 2011 2014 4 44 20 1 69.5% “mutually parted ways” Mike Holmgren Packers 1992 1998 7 75 37 0 67.0% resigned Red Miller Broncos 1977 1980 4 40 22 0 64.5% fired Marty Schottenheimer Chiefs 1989 1998 10 101 58 1 63.4% resigned Mike Ditka Bears 1982 1992 11 106 62 0 63.1% fired

The top coach on the list probably counts as a quasi-firing. Seifert left out of concerns he would be a lame duck coach when the 49ers refused to extend his contract before its final year, revealing their succession plan to hand the job over to Steve Mariucci. That’s not the case with Fox, who signed a three-year contract extension with the Broncos in April. The coach who preceded Collier in Cleveland was the legendary Paul Brown, who was fired by Art Modell in 1963 after 17 seasons and a .757 winning percentage. John Rauch left a dominant Oakland Raiders team in the AFL after a 33-8-1 (.798) stretch under interference from Al Davis in 1968. In the modern era, though, you can make a case that no coach won more frequently than Fox before being rewarded with a pink slip.

The other firings don’t really emulate what’s happening to Fox right now. Miller was fired by new Broncos owner Edgar Kaiser, a 38-year-old who wanted to hire a younger staff to match his own vigor. (He sold the team three years later.) Ditka had won a Super Bowl but was coming off a 5-11 season. Schottenheimer’s move might have been a quasi-firing, but he had just finished a 7-9 season (his first losing campaign in Kansas City). He quit before being fired by Modell in Cleveland as well, and while some of that may have come down to playoff failures, the Browns publicly claimed it was due to a disagreement about the team’s offensive coordinator, who happened to be Marty Schottenheimer.

Fox and Harbaugh will get lumped in together, at least for now, because they fit a roughly similar profile. They both took over flailing franchises and delivered immediate, sustained success, combining to make seven playoffs in eight years without producing a single losing season. Their departures both seemed unlikely at the beginning of their final season and yet seemed to make a lot of sense by the end of the campaign. Reports suggest that both Fox and Harbaugh had seen their relationships with their respective general managers fray, although I doubt there are many coach-GM partnerships in the NFL lasting more than a season or two where those reports wouldn’t be true, especially among successful teams that come up narrowly short of winning a Super Bowl.

I suspect that most people would perceive Harbaugh to be the better coach because he didn’t have Peyton Manning, and I can’t say I disagree. I was admittedly a harsh critic of Fox’s in-game decision-making during the TYFNC days. He made one of the worst challenges I’ve ever seen in 2013, exhibited an irrational aversion to early two-point conversions after his Panthers lost to the Patriots in the Super Bowl in part because of a failed two-point try, and famously sat on the football after the Rahim Moore Hail Mary with Peyton freaking Manning, 31 seconds, two timeouts, and a big-legged kicker in the thin air of Denver. As a tactician, Fox was brutal.

In-game decision-making is only part of the job, and the baseline for tactical nous as an NFL head coach basically assumes you’ll make decisions that hurt your team. Fox was hardly without his merits, especially on the defensive side of the football. He took over a defense that had allowed a league-high 471 points and had seven starters who were 30 or older, rebuilding it overnight. Ranked 30th in defensive DVOA that season, the Broncos improved to 18th in Fox’s first year and peaked as the fifth-best defense in 2012. After a 15th-ranked finish in 2013, the additions of veterans like DeMarcus Ware, T.J. Ward, and Aqib Talib saw the Broncos finish fourth this season.

The big names were one thing. Fox, along with defensive coordinator Jack Del Rio, exhibited an ability to mold draftees into useful contributors for the Denver defense. High draft picks like Von Miller, Derek Wolfe, and Rahim Moore delivered on their potential and quickly became impact contributors. Danny Trevathan was a sixth-round pick in 2012 who developed into one of the league’s better linebackers last season. Nate Irving filled in as a starting linebacker and impressed this season before going down with a knee injury. Bradley Roby had a disappointing game Sunday, but he looked promising during his freshman campaign, which isn’t often the case for even the best rookie cornerbacks.

Even more impressive was how successful Denver was in the bargain bin. Chris Harris went from being an undrafted free agent to making the Pro Bowl this season. Buy-low veterans like Shaun Phillips and Dominique Rodgers-Cromartie revitalized their careers and looked like their former selves under Fox. And while Del Rio probably deserves a good chunk of the credit for bringing in former Jaguars assets like Terrance Knighton and Brandon Marshall and getting the most out of them, they’re each playing far better in Denver than they were while Del Rio was in Jacksonville. Fox deserves some of the credit for that development process.

The future of the Denver coaches makes this story even more interesting. One of the first theories after the news of a possible Fox firing broke revolved around the idea that the Broncos would fire Fox to avoid losing one of their coordinators, both of whom had been interviewing for head-coaching gigs. Del Rio is considered the favorite for the Raiders job, as he’s expected to travel to Oakland for a second interview this week. Thirty-six-year-old offensive coordinator Adam Gase, meanwhile, has attracted attention from around the league in each of the last two offseasons; he’s also on his way to the Bay Area for a second interview, having emerged as a top candidate for the 49ers job.

It’s odd, then, that the Broncos don’t appear to be especially interested in keeping any of their coaches. Denver is reportedly allowing all of its coaches to pursue opportunities elsewhere. It’s not a surprise that the Broncos would let positional coaches and quality-control guys look for jobs out of common courtesy, but even with the outside interest in their coordinators, John Elway isn’t likely to promote his new head coach from in-house. If that’s true, this isn’t a reshuffling. It’s a clear-out.

Before you can even think about who might replace Fox, there’s the small issue of a franchise quarterback to consider. It’s still unclear whether Manning intends to return to the Broncos, but his comments after Sunday’s loss are telling. After being asked whether he was going to play for Denver in 2015, Manning gave a telling response. “I can’t answer every what-if circumstance,” Manning said. “What if you’re not as healthy? What if certain coaches leave? I can’t answer every what-if situation.”

There was never any talk of friction between Manning and his coaches, and while that doesn’t necessarily prove anything — the Broncos successfully hid Manning’s torn quadriceps from the world for a month — you can interpret Manning’s comments and this move in a couple of ways. If Manning didn’t want to start over with a new offensive coordinator, he might have wanted the Broncos to do whatever it took to retain Gase, even if it meant firing Fox and promoting Gase to head coach. The reports that the Broncos are willing to let Gase leave seem to suggest that isn’t true.

The alternative is that the Broncos see this offseason as a time of transition, which may also hint at the possibility of Manning leaving. If Gase also leaves, Manning would be starting over with a new coaching staff. He may very well lose either Demaryius Thomas or Julius Thomas to free agency, and Wes Welker is going to at least consider retirement after a year marred by concussions. Manning might view all the turnover as a good reason to retire, or the movement might be proof that Manning has already made up his mind.

If Manning does leave, I can understand Denver choosing to move on from Fox as part of a plan to bring in a coach with more patience for a semi-rebuilding project. Fox was able to successfully turn around a 1-15 Panthers team in 2002 and won seven games or more for eight consecutive seasons before collapsing back to 2-14 in 2010, but that was as a coach taking over at 47 years old. Fox will turn 60 next month, and coaches on that side of the mountain don’t often take on rebuilds. It’s not out of the question that it could work — Pete Carroll joined the Seahawks at 59 and that turned out OK — but if Fox knew that the Broncos were likely to be Brock Osweiler’s team next year, a mutual decision to leave might actually make sense for all parties involved.

Fox has already attracted attention from the Bears and Falcons, with Chicago seen as the heavy favorite to hire the onetime Giants defensive coordinator. It would be an understandable choice. The Bears weren’t competitive for most of 2014, but they do have a veteran roster and a defense desperately in need of refreshing after finishing 25th in 2013 and 28th this season. Fox has spent 20 years as a head coach or defensive coordinator and presided over defenses that were above league-average in DVOA during 18 of those seasons. The worst a Fox defense has ever ranked in DVOA is 19th. If new Bears general manager Ryan Pace thinks the quickest path to a turnaround is a defensive resurgence, Fox would be the perfect hire.

Denver’s choices if it doesn’t promote Del Rio or Gase to replace Fox aren’t exactly inspiring. Harbaugh has already joined Michigan. Rex Ryan, widely regarded as the best head coach on the market, agreed to terms with the Bills earlier this week. The hottest candidate leaguewide is probably Seahawks defensive coordinator Dan Quinn, whom the Broncos can’t interview this week. Bovada lists a pair of former Broncos coaches as the favorites, with Ravens offensive coordinator Gary Kubiak and former Washington coach Mike Shanahan as the leading choices. It would seem odd to fire Fox for failing to succeed in the playoffs before hiring Kubiak, who developed the same reputation during his time in Houston.

That’s what is at the heart of this Fox decision, the vague idea that the Broncos have gone as far as they can go with Fox without taking it to the next level and winning a Super Bowl. Maybe it’s true. My guess is that it’s impossible to really tell. You can make anecdotal cases in either direction. The Buccaneers fired Tony Dungy, who had gone 54-42 in revitalizing a moribund franchise, because he’d gone 2-4 in the playoffs. They hired Jon Gruden and won a Super Bowl the following year.

Then, Dungy went to the Colts and proceeded to go 48-16 in his first four seasons, only to go 3-4 in the playoffs, just as Fox has during his time in Denver. You could have made the same case for firing Dungy again in the hopes of sparking the team and bringing in a more aggressive coach. They didn’t fire Dungy, of course, and he won the Super Bowl with the Colts the following year. The Broncos might look back and find that they were right to move on from Fox, that his ceiling fell just short of where they wanted to be. They may also look back and find that he was one of the reasons why they came so close to getting there in the first place.