FOXBORO — Less than three years ago, Eric Mangini stood on the turf at Jacksonville’s Alltel Stadium on media day at Super Bowl XXXIX, reminiscing about his days as coach of the semiprofessional Kew Colts American football team in Melbourne, Australia, and the lunch that led to his becoming a low-level coaching assistant on Bill Belichick’s staff in Cleveland.

“I care about Bill deeply,” Mangini said that day. “I have nothing but absolute respect for him, and I can’t say enough good things about him. He’s an incredible guy.”

Back then, Mangini was the Patriots’ defensive backs coach, the baby-faced wunderkind who had survived season-ending injuries to Ty Law and Tyrone Poole. Days after New England’s Super Bowl win over the Eagles, Mangini would be tapped by Belichick to replace Romeo Crennel as defensive coordinator.

On that unseasonably cool day in northern Florida, Mangini rightfully gave Belichick much of the credit for his coaching knowledge and success.

Given that the final score is basically a foregone conclusion, there’s really only one concern when it comes to today’s Patriots-Jets game:

Which will be colder — the windy, rain-filled air in Foxboro or the reception Eric Mangini gets from Bill Belichick for the postgame handshake?

Will there even be a handshake?

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IT’S HARD TO IMAGINE Belichick and Mangini’s relationship having devolved to this point.

After his time in Melbourne, where he went as part of a study-abroad program while attending Belichick’s alma mater, Wesleyan, Mangini wasn’t ready to become an investment banker; thanks his dalliance with coaching in Australia, he wanted to stick with football. Former Wesleyan coach Kevin Spencer was on the coaching staff of the Browns under Belichick, and Mangini had his in.

While Mangini’s early role in Cleveland is a bit cloudy — he was either a ball boy or public-relations gopher, depending on who’s telling the story — he found himself sitting across from Belichick at a training camp lunch table.

By the end of training camp, Mangini was a coaching assistant.

“We got to a point where we would have kicked him out and sent him home, but from dealing with him, we were all pretty impressed with his work ethic, with his attention to detail, his interest in coaching in football, et cetera,” Belichick has said.

After that season, Belichick was fired and the Browns moved to Baltimore. Mangini stayed with the franchise and spent a year with the Ravens as a quality-control/offensive assistant before reuniting with Belichick on the Jets’ staff.

When Belichick got the job in New England, he brought Mangini north with him.

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IN HIS BOOK Patriot Reign, Michael Holley painted perhaps the best picture of the relationship between the two men. The Patriots, wrote Holley, have a vigorous and demanding work environment where each employee is expected — indeed, demanded — to strive toward excellence. Mangini wasn’t afraid to express his opinions to Belichick or disagree with him, sometimes heatedly. But that’s what Belichick wants from the people who work for him, and Holley wrote that they could be arguing one minute and laughing the next. That relationship lasted until Mangini left — for the Jets of all teams.

Stories abound as to the causes of the rift. One is that Belichick’s distaste for the Jets — the team he left in 2000 to join the Patriots, with his departure so bilious that one Jets executive reportedly questioned his mental stability — was so strong that he urged Mangini not to take the job, and was angry that his advice wasn’t followed.

That seems far-fetched, since Belichick has never been one to stand in the way of his assistants moving on to bigger positions; another, more believable, theory is that Mangini, while still under contract to the Patriots, attempted to convince some Pats coaches and a few free-agents-to-be on the New England roster to follow him to New York. (One, linebacker Matt Chatham, did leave the Patriots to sign with the Jets, and wide-receivers coach Brian Daboll left Foxboro to join Mangini’s staff.) Since no one on either side of the fence will discuss exactly what happened, that’s all these are: theories.

In any case, Belichick had Mangini locked out of Gillette Stadium. The assistant he had mentored and groomed for 10 years wasn’t allowed back in to collect his personal items.

It was only the beginning.

Before their first meeting as rivals in September 2006, Mangini referred to Belichick as a friend. Belichick didn’t refer to Mangini at all, passing up numerous opportunities to praise or even acknowledge his former assistant except in the most generic of terms.

When the game — a 24-17 Patriots victory at Giants Stadium — ended, a wordless Belichick gave Mangini a cold, perfunctory handshake before quickly turning and walking away. The handshake became the postgame topic of conversation, especially in New York.

“I don’t care,” Belichick responded a few days later when asked about it. “You can scrutinize it all you want. Knock yourself out.”

But it was right around that time that the Pats filed tampering charges against the Jets for their contact with holdout wide receiver Deion Branch, who had received permission from the Patriots to talk contract terms with other teams. The Jets were eventually cleared of the charges by commissioner Roger Goodell, but it further poisoned the atmosphere between the clubs . . . and, apparently, their coaches.

That atmosphere didn’t get any clearer when the Jets upset the Patriots in the mud and slop at Gillette Stadium in November (the last game before the Pats finally tore up the field and replaced it with an artificial surface). And when Mangini preempted Belichick’s attempt for another bump-and-run postgame handshake by grabbing his former boss’ arm and shaking it firmly, yet another round of armchair psychology was unleashed in the media.

It finally ended — or so we thought — when the Patriots beat the Jets in the first round of the playoffs and Belichick embraced Mangini in one of the most awkward hugs in history.

Then came Spygate.

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IN NEW ENGLAND, it’s been seen as a case of an ungrateful pupil dropping a dime on a mentor to whom he owes everything over an act so common in the National Football League that Goodell had to send a memo to every team to get it stopped. But everywhere else — and, again, especially in New York — it’s been seen as vindication, proof that the Patriot “dynasty” was built on the sand of arrogant, unethical behavior of the team in general and Belichick in particular, brought to light by someone with inside knowledge of New England’s Machiavellian ways.

That viewpoint seems a stretch, especially in light of the Pats’ dominance this season. (The taping stopped in the first quarter of the first game, so it’s hard to attribute what’s happened in the 51 quarters since then to “cheating.”) But it’s found traction. The references are everywhere, such as when Garo Yepremian, the kicker on the 1972 Dolphins — the only team so far to go through a season undefeated — saying the Pats should “bring their camera with them to the Hall of Fame” if they finish 19-0.

And that’s been the true fallout of Spygate. Even more than the loss of a draft pick and fine levied on the organization, even more than the half-million dollar fine Belichick suffered, the biggest blow was the hit that Belichick’s reputation took, as the validity of his three Super Bowl titles with the Pats have been called into question. Even if the Patriots do finish unbeaten and win the Super Bowl, the stain of Spygate will, rightly or wrongly, always be attached to the achievement, at least in the near future. It remains to be seen how history will ultimately judge all this.

Either way, who was at the base of it all? Eric Mangini.

Who would have thought it, three years ago in Jacksonville?

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IT DIDN’T END with Spygate, either. The latest dustup was last week’s revelation that the Jets had a camera operator removed from a perch above the north end zone at Gillette Stadium during last year’s playoff game, with Mangini claiming the Jets had received permission from the Patriots before the game to have him there and Belichick countering by saying no permission had ever been granted.

All season, the theory was floated that the Pats — already accused of running up the score on overmatched opponents — would unleash a season’s worth of fury on the Jets today; after all, the players’ accomplishments in winning the three Super Bowls was also called into question. One wag suggested the Krafts would need to install an NBA-style scoreboard to total up the points.

But the wind and rain and ice and snow that’s expected today may do what opposing defenses have failed to do all season: Slow down, or even stop, an explosive New England offense that’s in the process of rewriting the NFL record book. And wouldn’t that be the ultimate story twist: Mother Nature lending Mangini a hand. People who’ve already fitted Belichick with devil’s horns and a red tail would have a field day with the symbolism.

The drama heading into today is just delicious. Absurd, maybe. But delicious.

As for that handshake: Belichick was asked about the postgame ritual on a couple of occasions this week, and claimed not to have given this particular one much thought.

“Right now our focus is on the Jets and the game, and not on the high-fives and cartwheels and backflips,” he said.

In other words, don’t expect one.

smanza@projo.com