MINNEAPOLIS — Crack open a door and peer inside the clubhouse of the loathed and envied New England Patriots, and what you find are a lot of surprisingly smallish men who exude more anxiety than swagger.

“The key is just make sure you don’t get fired each day you come to work,” said defensive captain Devin McCourty, a safety who stands 5-foot-11 with the help of thick-soled sneakers. There are only two real giants, Tom Brady and Bill Belichick, in the room, but of course they’re the team leaders in the neurotic fear of failure that is the fuel of the franchise.

The partnership between the perfection-crazed quarterback Brady and the detail-obsessed coach Belichick is a “perfect storm,” as former coach Tony Dungy puts it — a centrifugal electromagnetic vortex that attracts heavy metal: eight trips to the Super Bowl in 17 years, five of them resulting in silver trophies.

“I’d hate me, too,” Brady said wryly last week.

Underlying their accomplishments is not ambition so much as an epic neediness. Winning for them is a need, and there is nothing to suggest that, should they win a sixth championship when they meet the Philadelphia Eagles on Sunday, it will soothe them into not needing a seventh.

“Winning became an addiction,” former Patriots linebacker Tedy Bruschi said. “It’s that way for Tom; it’s that way for Belichick. They’re the same. It’s never enough.”

Such an addiction that Brady, the 40-year-old father of three, is compulsive about even the causal games of “Trashketball” that the Patriots habitually play at their stadium in Foxborough, Massachusetts. There are no end of stories about how this perplexing, dimpled man who has everything still issues guttural screams in search of primacy. When they skim Frisbees into a bucket, “you’d have thought it was the Super Bowl,” center David Andrews said.

During walk-throughs going over concepts for a game, Brady will amuse himself by throwing a hard rubber ball downfield at the covered electrical outlets buried in the margins of the field, trying to bounce it off the metal so it hits a receiver in the numbers. “If he misses, he acts like somebody ran the wrong route,” special teamer Matthew Slater said. The stories of Brady’s unhinged competitiveness growing up in California are by now well-known — “I wrecked a few game controls,” he admitted. Less known is that he will still hurl a board game across the room as an adult.

As with any addiction, they can barely enjoy the fix for long. Even last year, on the morning after their fifth title, Belichick was fretful that their run through the playoffs had cost him precious time in preparing for the next season.

Such constant, twitchy discontent doesn’t come without its stresses, obviously. ESPN reported in January that there was a rift between Belichick and Brady over a range of chafing issues, from Brady’s insistence on trying to play to the age of 45 and his hypnotic reliance on his unconventional “body coach,” Alex Guerrero, to Belichick’s longtime habit of awarding credit only grudgingly. Brady was weary of Belichick, it was said, and vice versa.

Though Patriots officials denied the most serious conclusion — that Belichick was frustrated enough to quit — the overall theme seemed correct: Two compulsive personalities don’t always coexist easily, especially after 18 years of wearing on each other.

As Brady admitted last year, Belichick “coaches us hard. There’s some throws that I make and you throw it 50 yards downfield and hit the guy in stride, and I’m like, ‘Damn, that was a pretty good throw.’ And I’ll look back at him, and he’ll be looking for the next play.”

A certain distance and withholding is a fundamental aspect of their dynamic; they’ve never had a social outing. But that tension is the constant around which everything else revolves, a high-pressure cell that holds the center of the storm together. An ever-shifting cast of characters has swirled around Brady and Belichick, who have been together for so long now that Danny Amendola was 16 when they won their first ring in 2002.

It doesn’t seem to matter who is on the 53-man roster from year to year; the basic standard of play never varies.

“They make minimal errors,” former Tennessee Titans coach Mike Mularkey said. “They make the opponent do the damage to themselves.”

That is less about physical dominance than a mentality. There’s only one player on the Patriots’ roster who is so physically imposing that he keeps the opposition awake at night, and that’s 6-foot-6 tight end Rob Gronkowski. Most of the rest are guys like Amendola, the 5-11 wide receiver who was an undrafted free agent and whom the Dallas Cowboys and Philadelphia Eagles couldn’t find any use for.

Maybe it’s because Belichick himself was an effort-over-talent player, a center and tight end at Wesleyan whose coaches told him, “Got a long way to go, buddy.” For whatever reason, it’s striking that fully a dozen of New England’s key players stand shorter than 6 foot. (By way of comparison, their AFC championship game opponents, the Jacksonville Jaguars, had just seven on their entire roster).

Belichick likes to say, “It’s not the best 53; it’s the right 53.” While other coaches measure height and weight and scores in agility drills, Belichick seems to measure something else: for lack of a better term, athletic heart. Over and over again, he finds the Amendolas, the discarded who grow into vital role players and big-game contributors.

“We beat the bushes for them,” Belichick said.

“Obviously, coach Belichick and his staff have an idea in their minds of, ‘This is what a Patriot is,’” Slater said. “But I don’t know how they identify it. I just know they find a lot of them. It’s hard to last around here if you can’t keep up mentally.”

Once they are in the door, the indoctrination begins. “I hope my expectation for you guys isn’t better or more than your expectation for yourself,” Belichick will say. Slater experienced the brainwashing as a rookie fifth-round draftee in 2008. He was playing safety on the scout team one afternoon when he was directed to give the offense a certain look. He did it sloppily. On the sideline, all-pro linebacker Mike Vrabel couldn’t stand to watch. He yanked Slater off the field, took his spot on the practice squad and ran it right.

“Here was a guy in his 12th year that was so committed to the team and the team’s success that he was going to get in there with the scout team and do it,” Slater said. Since then, Slater has made seven Pro Bowls for his special teams play.

It’s easy to forget now that Brady was once one of those players just scrambling for a place. And it’s an interesting exercise to look back at Belichick’s perceptions in 2000 when he picked up Brady in the sixth round of the draft, spotting in the 199th player chosen something so many others missed. Belichick said he saw “good value” in him, a “good, tough, competitive, smart quarterback.” A few months later, when Brady entered the lineup because of starter Drew Bledsoe’s injury, Belichick said, “I really don’t think that I’m going to be standing here week after week talking about all of the problems Tom Brady has.”

That’s about the highest praise Belichick has ever doled out to Brady publicly. Unquestionably, it’s been convenient and made Belichick’s coaching job immeasurably easier to have a star quarterback who is perpetually the team’s most consumed striver.

Even now, Brady is chronically worried. He’s not just worried about aging, and the effects of inflammatory foods or sugars. He’s not just worried about balancing his career with marriage and fatherhood. He’s worried about the most basic thing: his throwing mechanics.

“You know, throwing the football is a skill,” he said Thursday. “You have to work at it. If you start at 100 percent and your mechanics go off by 2 percent a week, then you look up at eight weeks into the season, and you’re 15 percent off. And that’s a big difference between winning and losing.”

Contained in that statement is all you really need to know about the Patriots, about their exactingness, and the degree to which they convince themselves that, no matter how much they win, they are always playing from behind.

“Brady and Belichick, those are self-made men,” Bruschi observed. Threatened by failure has become their default position and daily motivation: Their slogan is “Not Done.”

Of course, it’s the pursuit that they love, as much as the winning. You sense that what really satisfies them is not the trophy so much as the continuous keyed-up-ness, the keenness they feel from the never-ending sculpting project. It’s the only thing that explains their refusal to self-congratulate, to accept ease or to become slack, to relax into their success. And it’s what really separates them.

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