NFL

How the Giants plummeted from contenders to 0-6

Thanks to the 21-year reign of the salary cap, you won’t find much shock value in an NFL season anymore.

Franchises still rise to dominance, but every one of them eventually finds it too complicated and expensive under the cap to stay very long or even think about uttering the word “dynasty.”

And quick turnarounds happen so frequently in the cap era that a team going from 2-14 to division champion in one year now prompts little more than a shrug.

Until the 2013 Giants came along, that is.

Now 0-6 after Thursday night’s 27-21 loss to the Bears, Big Blue has seemingly done the impossible — caused jaws around the league to drop at the spectacle of their complete implosion.

It would be difficult to find anyone connected to the sport — coach, executive, player or scout — who could say with a straight face that they saw such an utter meltdown coming just 20 months after much of the same Giants cast won the Super Bowl for the second time in just five years.

“What’s happening with the Giants is what you call a total shock,” said longtime NFL draft expert Gil Brandt, one of the architects of the Cowboys’ great teams of the 1970s. “Nobody in their right mind would have predicted them to fall apart like this and to do it this fast.”

A consistently respectably team morphing into a bottom feeder isn’t unprecedented in the NFL, of course. But it’s the speed and apparent totality of Big Blue’s meltdown that has so many around the league scratching their heads in amazement.

How does a team with a proven GM in Jerry Reese, one of the NFL’s most respected coaches in Tom Coughlin, a two-time Super Bowl MVP quarterback in Eli Manning and a proven, veteran supporting cast become a punch line practically overnight?

“You won’t find many people who think the Giants aren’t a smart, well-run organization,” an NFC GM told The Post. “For them to be [0-6] just shows you that the competitive balance is so narrow in this league that it only takes one or two strings now for the whole thing to fall apart.”

Though the reasons for the Giants’ worst start since 1976 are numerous, conversations with numerous NFL insiders and observers this week point to three main culprits.

ELI AND THE FLAT CAP

Giants co-owner John Mara was one of the architects of the league’s lopsided victory over the players in the 2011 labor negotiations, so it’s ironic that one outcome of that messy fight — a lower and flatter salary cap — is playing the biggest role in his team’s downfall.

The cap is just $123 million per team this year, an increase of less than $3 million from 2012. It’s also the same amount this season as it was in 2009 — the last year the NFL operated with a cap before the lockout.

Most experts also predict the cap to remain relatively flat over the next two years, rising to no more than $127 million per team during the 2015 season.

Reese actually has done a good job of managing the Giants’ cap since he took over for Ernie Accorsi in 2007, keeping much of the core of two world champions together without mortgaging the future or compiling a lot of “dead money” — cap space devoted to players no longer on the team.

The Giants have just $7.3 million in dead money this year, ranking them 21st in the league and a far cry from the Jets and their $22 million in wasted 2013 cap space — third-most in the NFL.

But bad timing has turned the seven-year, $106.9 million contract extension the Giants gave Manning in 2009, which seemed manageable before the new labor agreement, into an albatross in light of the flat cap and his dreadful play the first six games this year.

As well as boasting the largest cap figure of any player in the NFL this season at $20.85 million (almost $3 million more than brother Peyton), Manning is taking up a whopping 17 percent of the Giants’ entire 2013 cap by himself.

The huge share devoted to Manning is a big reason why the Giants weren’t able to retain two key Super Bowl pieces in defensive end Osi Umenyiora and running back Ahmad Bradshaw this past offseason. Manning’s contract also is why Reese and the Giants rarely have been more than bargain hunters in veteran free agency each spring.

In return, Manning has thrown an NFL-most 15 interceptions in the first six games this season and ranks near the bottom of the league with a career-low 64.0 passer rating.

And unless Manning restructures his contract to free up cap room, which would mean the Giants extending their commitment to him even further, he will hog their cap for the next two years, too, with scheduled cap figures of $20.4 million in 2014 and $19.75 million in 2015.

“When you have a franchise quarterback taking up that much of your cap, it forces you to be creative because you’ve got 52 other [roster] spots to fill,” former NFL agent Joel Corry said. “That also means your franchise quarterback has to play well, too.”

Manning isn’t the only highly paid Giant underperforming this season. His cap figure combined with the cap numbers of just four other players — safety Antrel Rolle, defensive end Justin Tuck, cornerback Corey Webster and center David Baas — is consuming 38 percent of the team’s entire cap.

What has all of that gotten the Giants? A top-heavy roster under the cap, the league’s worst record and the agony of their horrified fans.

DECLINING DRAFTS

Reese’s draft skills have been celebrated since his entire seven-player class in 2007 not only made the team but contributed significantly to the Giants’ stunning run to the Super Bowl that year.

Reese’s deft hand continued through 2010, when his first two picks — defensive end Jason Pierre-Paul and defensive tackle Linval Joseph — proved key pieces in a defensive line that led the way to another Lombardi Trophy the following season.

But Reese’s fastball has all but disappeared in the meantime.

Of the 22 players drafted by the Giants since 2011, just three began this year as starters — running back David Wilson, right tackle Justin Pugh and cornerback Prince Amukamara. And Wilson, whose early fumbling woes got him benched, might miss the rest of the regular season after a narrowing of his spinal column was discovered this week.

An even longer look isn’t flattering, either. Although wide receiver Victor Cruz proved an undrafted gem, Pierre-Paul is the only Reese pick out of 45 selections over six drafts since his 2007 goldmine to make the Pro Bowl.

And the Pierre-Paul choice isn’t looking like such a grand slam anymore, either. Beset by back woes, he went from 16 1/2 sacks in 2011 to just 6 1/2 sacks last season and a mere one sack in six games this year.

With plenty of high picks (and potentially the No. 1 overall choice) in 2014, Reese might need to repeat his 2007 draft masterpiece to restore a reputation that has suffered with every ugly loss this year.

“When you’ve got a franchise [quarterback] to pay and you don’t have a lot of money for [veteran] free agents, you’d better hit on your picks,” an AFC personnel director said. “The Giants haven’t done that much lately.”

BAD BREAKS

Nothing can hasten a team’s demise like injuries, and the Giants and Steelers — another proud and successful franchise off to a winless start — have been NFL poster boys for that this season.

In the Giants’ case, safety Stevie Brown’s season-ending torn knee ligament in the preseason took away a key defender responsible for eight interceptions and two fumble recoveries last season while also starting their injury tidal wave.

Brown was joined in short order on injured reserve by running back Andre Brown, middle linebacker Dan Connor, fullback Henry Hynoski, guard Chris Snee and cornerback Aaron Ross. All were either starters or expected to play major roles for Coughlin’s team this season.

“It’s been like a perfect storm for the Giants, and not in a good way,” said Corry, the former agent who is now an NFL cap analyst. “The injuries have been bad, but Eli’s just been dreadful.

“When you have a great quarterback, that can cover up a lot of things,” Corry continued. “But Eli hasn’t even been average — he’s been awful. All of that can get you to [0-6] really quick.”

But if it’s any consolation to Reese or Coughlin, many around the league don’t expect the Giants’ stunning fall to be permanent.

Manning’s contract is an issue, of course, and could force some interesting decisions if the Giants end up in position to take highly touted Louisville quarterback Teddy Bridgewater first overall.

The future of Coughlin and especially offensive coordinator Kevin Gilbride and defensive coordinator Perry Fewell also will be a hot topic unless Big Blue can somehow right the ship in the final 10 games.

But in terms of the roster, Reese actually has the Giants in good position cap-wise for 2014 and beyond. They are projected to have just 33 players under contract for roughly $106 million next spring (when the cap is expected to be around $125 million) and could save an additional $20 million in cap room if Snee retires and Rolle, Webster and disappointing free-agent tight end Brandon Myers are released.

Who knows? The Giants might be the NFL’s latest one-year turnaround this time next year, and it’s not as if their two most recent Super Bowl crowns were predictable, either.

But for the time being, the cap is flexing its muscle at the Giants’ expense while they endure the consequences of too many bad decisions and bad breaks.

“Everybody goes through this in some form or another,” Gil Brandt said. “It’s just the Giants’ turn now, and they’re going to have to grin and bear it.”