It’s long been said the NFL stands for Not For Long. Change comes quickly in a copycat league where winning strategies are examined, analyzed and imitated and constant innovation is central to continued success. But even by that standard, it’s difficult to recall a more rapid fall from grace than what’s gone down with the Philadelphia Eagles over the past two months.

The Eagles were the envy of the league as recently as seven weeks ago, a winning machine fronted by an energetic young coach, ascendant franchise quarterback and one of football’s most talented rosters from top to bottom. After romping to last year’s NFC championship and coming up three points short of winning the Super Bowl, they’d raced out to the NFL’s best record at Thanksgiving and appeared on course for a return trip to the sport’s biggest stage.

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But from that 10-1 start, the Eagles came undone and limped into Monday night’s NFC wildcard playoff having dropped five of six games – a death spiral punctuated by blowout losses to the 3-12 Cardinals and 5-11 Giants. All of it came to a merciful, predictable end on a muggy Monday night at Raymond James Stadium, where they were dog-walked 32-9 by a mediocre Tampa Bay team they’d dominated in October – a horror-show scoreline that could have been far worse had the mistake-prone Buccaneers not dropped about a half-dozen passes. The Eagles couldn’t block. They couldn’t catch. They certainly couldn’t tackle. They were unprepared, unmotivated and uninterested. In a key sequence freighted with unmistakable metaphor, the Tush Push – their trademark short-yardage play once hailed as unstoppable – was stuffed at the goalline.

The Eagles have experienced their share of home-stretch faceplants in a nine-decade history filled with far more heartbreak than glory – 2014 under Chip Kelly, 1994 under Rich Kotite, 1981 under Dick Vermeil and 1961 under Nick Skorich – but none of those collapses can compare to the warp-speed regression of the past seven weeks. This year’s side became only the second team in NFL history to fail to win 12 games after a 10-1 start, joining the 1986 New York Jets. But even those Jets conjured enough pride while in freefall to squeeze out a playoff win. Not these Eagles, who suffered their second-biggest postseason loss ever, against a bottom-10 offense helmed by a journeyman quarterback.

Two months ago, it would have been unfathomable to imagine the Eagles parting ways with Nick Sirianni, the 42-year-old wunderkind who in two and a half seasons had amassed the best win-loss percentage of any current NFL head coach and appeared on deck for a fat contract extension. After the most spectacular in-season unraveling in NFL history, it’s almost harder to imagine the alternative.

So what happened? Let’s start with the obvious. After last year’s Super Bowl run, Philadelphia saw both of their coordinators poached for head coaching jobs: OC Shane Steichen to the Indianapolis Colts, DC Jonathan Gannon to the Arizona Cardinals. Those vacancies were filled by Brian Johnson and Sean Desai, respectively, and it was clear that the replacements were in over their heads from early on.

The once-formidable pass rush that flirted with the NFL all-time sacks record last year – and which lost key players Javon Hargave, CJ Gardner-Johnson and TJ Edwards to free agency – regressed badly despite general manager Howie Roseman’s investment of more capital space and draft resources on the defensive line than anywhere else. That spending was intended to conceal deficiencies at linebacker, cornerback and safety, holes that proved too big to patch schematically, especially when the secondary was hit by injury early in the season.

Hurts, the MVP runner-up a year ago who played through a dislocated finger on Monday night, injured his knee in October and never fully recovered. Johnson’s maddening refusal to run the ball, despite an offensive line tricked out with future Hall of Famers and a Pro Bowl-caliber running back in D’Andre Swift, persisted all season.

In short, they had big problems. And when it came time to fix them, the coaching staff had no clue what to do. Once that became clear to the players, it was over.

None of that can directly account for Philadelphia’s golden start to 2023. And it’s true: the Eagles raced to the NFL’s best record at Thanksgiving weekend and the inside track on the No 1 seed, piling up wins over Tampa Bay, Kansas City, Miami, Buffalo and Dallas, all of whom ended up in the playoffs. But rather than recognize their gaudy record benefited from a luck factor that defied analytical scrutiny – seven of those wins came in one-score games – the coaching staff deluded themselves into the canard that winning DNA and organizational culture would see them through. They knew how to win.

But the house of cards came crashing down in early December when they hosted San Francisco in an eagerly anticipated rematch of last year’s NFC title game. The Eagles surrendered touchdowns on six straight drives – 85 yards, 90 yards, 75 yards, 77 yards, 75 yards and 48 yards – in a 42-19 defeat that kickstarted their demise. It was a bitter pill for Philadelphia, who’d listened to months of trash talk from San Francisco’s star players about how the Eagles were overrated frauds. But in the end the Niners were right about everything, totally saw through Sirianni and – unlike most every other team in the NFL to that point – exposed them badly.

Like the champion prize-fighter who’s never the same after that first knockout loss, the Eagles lost something that afternoon they’d never get back. San Francisco laid down a blueprint, but the coaching staff’s lack of response made it far too easy for future opponents to follow. (The Eagles’ inability to scheme a blitz response for two months, for instance, reflects an incompetence rarely seen at the NFL level.) They were blown out the next week at Dallas and only went south from there, their once-stout defense regressing into a blur of blown assignments, busted coverages and whiffed tackles. In a move that stunk of desperation, Sirianni replaced Desai as defensive coordinator with Matt Patricia, a retread whose primary claim to fame – certainly in Philadelphia – was overseeing the Patriots’ defense that surrendered more than 500 yards to the Eagles in their first and only Super Bowl win.

There’s no shortage of blame to go around. Some may question how the leadership among the players on the team was so bad to allow this outcome. Others may counter that the coaches gave the players no chance to win. Either way Philadelphia’s stunning implosion amounts to a missed opportunity that will haunt this football-mad city for years.

The obvious answer is cleaning house. The entire coaching staff must go with the exceptions of offensive line coach Jeff Stoutland and special teams coordinator Michael Clay, whose once-shaky unit demonstrated marked improvement from 2022.

As for Sirianni, it may not be that simple. His win-loss percentage remains the best in club history, even accounting for this year’s catastrophe. No other Eagles coach has ever reached the playoffs in each of his first three seasons, a body of work that suggests he’s earned one more crack. It would certainly represent a break in type for team owner Jeffrey Lurie, whose even keel and resistance to reactive moves has been a source of pride over his three-decade ownership.

But make no mistake: the Eagles find themselves at a crossroads that would have seemed unfathomable not that long ago.