The local pigskin punditry is twisting itself into logistical knots trying to come up with the reasons for New England’s inconsistent 3-2 start.

Let me put an end to the mystery. The problems with the Patriots can be summed with six words: Bill Belichick has lost his mojo.

Even worse? The whole league knows it — as the Broncos proved on Sunday.

It’s not politically correct in pigskin circles to declare Belichick’s mojo a vestige of a glorious earlier era of the NFL, like Sammy Baugh’s leather helmet or Johnny Unitas’ black high-tops. It’s certainly not welcome among Patriots fans. But the blasphemy of the claim doesn’t make it any less true.

It’s been years — five to be exact — since teams feared facing a Belichick defense or quarterbacks feared staring into the blinding maelstrom of a Belichick scheme.

It’s been five years, not too coincidentally, since the Patriots hoisted the Lombardi Trophy.

In 2005, we thought it was just a bad year when the Patriots ranked 27th in defensive passer rating (87.8) — the single most important measure of defensive success.

In 2006, we considered the historic defensive collapse against the Colts in the AFC title game one of those once-in-a-lifetime events. But it turns out it was just a precursor of things to come.

In 2007, we focused the blame on the offense that tanked in the Super Bowl and not on the fact that, for the second season in a row, the pass defense couldn’t make a single stop in the fourth quarter of the biggest game of the year.

In 2008, we had the convenient excuse of Tom Brady’s injury to mask the fact that the pass defense was among the worst in football (89.8 defensive passer rating, 23rd).

But here in 2009, the pass defense is literally worse than ever — a 92.5 defensive passer rating — and we’re running out of excuses for the Patriots and for the once-unbeatable Belichick system.

It wasn’t always like this. Back in his heyday, first with the Giants and later here in New England, Belichick had a gift for shutting down the best quarterbacks and the best passing games the league could throw his way. He earned his chops humiliating the likes of legends such as Joe Montana and Peyton Manning in the playoffs. He was at his best in the biggest games, disarming the K-Gun in one Super Bowl and closing the curtain on the Greatest Show on Turf in another.

But these days, even a humble journeyman like Kyle Orton finds that he can shred Belichick defenses as if they were Bernie Madoff balance sheets.

Heading into their game against the Patriots on Sunday, the Broncos had benefitted from a fairly balanced offensive attack. They had attempted 127 runs while dropping back to pass 125 times in their first four games.

But looking at what he knew was a sub-standard Patriots pass defense, Josh McDaniels and his staff abandoned that balance and let Orton pass wild. In fact, it was a historic day for the Broncos quarterback.

Orton set career bests in both attempts (48) and completions (35), while his 330 yards fell just 4 yards shy of another career high. For the record, he posted that 334-yard effort last year against a Lions team that set an NFL record for incompetence with a 110.8 defensive passer rating — literally the worst pass defense in the history of football.

But that’s the kind of company in which the once-feared Patriots pass defense finds itself these days. And, for the fifth year in a row, an ineffective pass defense is likely to ruin the team’s Super Bowl hopes — even as the local pigskin “pundits” fret over trivial mishaps such as a missed connection from Brady to Wes Welker.

The statistical anchor for this team is the fact that the Patriots can’t keep opposing passers out of the end zone and they find it increasingly difficult to come up with interceptions — those game-changing plays that are critical to success.

As noted here in the past, every INT a team makes improves its chances of winning by a full 20 percentage points. So, a failure to come up with picks is a huge handicap for any team to overcome.

The Patriots surrendered 27 touchdown passes last year — 31st in the league — while picking off just 14 passes.

This year, they’ve surrendered seven TDs through the air (a small statistical improvement) but have picked off just two passes (a dramatic statistical decline for an already bad unit). In fact, no defense in football has grabbed fewer picks than the Patriots. 

That’s 34 touchdowns through the air against New England in the last 21 games, with just 16 picks. You simply cannot and will not win consistently in the NFL surrendering two touchdown passes for every INT.

No team ever has won consistently with a pass defense this bad and let me be the first to tell you that no team — not even Tom Brady’s Patriots — ever will.

To understand the dramatic downfall from the glory days, look at the 2003 Patriots, who fielded the best defense in franchise history: They surrendered 11 passing TDs all year, while hauling in 29 INTs. That’s a dramatic difference from the Patriots defenses of more recent vintages.

Let me put the struggles of the Patriots pass defense in a framework that every football fan can understand. Let me compare it to the much-maligned defense of the Colts in the years since the Patriots last won a Super Bowl. Now, in the often-incorrect circles of conventional wisdom, the Patriots always have a better defense than the Colts. But the Cold, Hard Football Facts say otherwise.

Here’s how the two teams stack up in the critical defensive passer rating category each year since 2005.

Defensive passer rating simply takes the formula used to measure quarterbacks and applies it to pass defenses. It’s had an extraordinarily high correlation to team success literally since the beginning of the modern offense in 1940 and is probably the single most important measure of defensive success. Keep in mind that a passer rating of 80 is about average in the modern game. So the Colts have been generally above average since 2005; the Patriots generally below average.

New England’s pass defense also suffered memorable collapses in the 2006 and 2007 playoffs. Indy’s defense improved dramatically during its postseason Super Bowl run in 2006.

But Belichick’s biggest failure is probably not in his schemes in the autumn, but in his drafts in the spring. The organization has not drafted an impact defensive back since Asante Samuel in 2003 and has not uncovered an elite pass rusher since, well, ever. The Patriots seem content to forego elite pass rushers in the draft as a matter of strategy.

But Belichick desperately covets elite defensive backs — as evident by the 12 draft picks (out of 51 selections) devoted to the position over the six years since Samuel, now with the Eagles, was selected. But not one those 12 picks has proven an impact player. In fact, few even made the team or even play in the NFL today.

Belichick, in other words, has whiffed badly in the past several drafts, and it has shown up in the team’s inability to defend the pass in recent years.

The draft failures have a ripple effect. With one of every four picks in the past six drafts devoted to DBs who failed to deliver, the Patriots have also inhibited their ability to improve other aspects of the team.

I don’t care if your offense features Tom Brady and Randy Moss or Joe Montana and Jerry Rice — you simply don’t win games when you can’t stop the other team through the air.

And it’s been years since you could count on a Bill Belichick defense to stop the other team through the air or come up big in the big game.

Hell, it’s tough enough these days just trying to contain the Kyle Ortons of the world, let alone the Peyton Mannings.