Metro

How Jeter put A-Rod in the Yankees’ ‘snubhouse’

(
)

It was a true bromance — until it went foul.

Frenemies Derek Jeter and Alex Rodriguez have spent the past decade taking swings at each other, according to a new unauthorized Jeter biography that shows the splintered relationship was nastier than ever reported and that Yankees brass thought it threatened to fracture the team — and even cost it money.

“The Captain,” by sportswriter Ian O’Connor, out next month, chronicles the bond between the Yankees stars — a soap-opera saga filled with power and betrayal — from their days as rookies playing for different teams but as close as brothers, to their icy co-existence in The Bronx.

PHOTOS: DEREK JETER & A-ROD THROUGH THE YEARS

Jeter’s unyielding insistence on loyalty and his dislike for A-Rod during the third baseman’s early years in pinstripes was so legendary that one Yankees official admitted he was too scared to talk to Jeter about making amends with his teammate.

“It would’ve been the last conversation I ever had with Derek,” the official said. “I would’ve been dead to him. It would’ve been like approaching Joe DiMaggio to talk to him about Marilyn Monroe.”

Don Mattingly, then the hitting coach and former captain, tried to intervene, citing his own unfriendly history with teammate Wade Boggs.

“I faked it with Boggs,” he told Jeter. “And you have to fake it with Alex.”

Jeter, now 36, was a Yankees farmhand and A-Rod, 35, a Seattle Mariners first-round pick when they met at a Michigan-Miami baseball game in 1993 — introduced by agent Steve Caruso, who found A-Rod was already fascinated by Jeter.

The pair had plenty in common — both were young, ambitious shortstops on the cusp of superstardom — and split their time between A-Rod’s place in Seattle and Jeter’s Upper West Side apartment. They appeared together on the cover of Sports Illustrated in 1997.

They were so close, they became targets of teasing.

“Are you going over to your boyfriend’s house?” major-league first baseman and former high-school teammate Doug Mientkiewicz needled A-Rod.

Yankees slugger Jim Leyritz once had to remind the rookie Jeter, “Hey, dude, he’s on the other team.”

By 1998, A-Rod had become privately jealous of Jeter’s rising star — his ranking among People magazine’s Most Beautiful People, his endorsements, his fan following, the book says. A-Rod was considered the better overall player, but Jeter was getting more ink.

The breakup came in 2000. A-Rod, playing for the Texas Rangers after signing a historic, 10-year, $252 million contract, made a series of public comments that rankled a thin-skinned Jeter, who was in the midst of negotiating his own massive deal (he signed a 10-year, $189.5 million contract a year later).

“He just doesn’t do the power numbers,” A-Rod explained to an ESPN radio interviewer on why he was paid more than his pinstriped pal. “And defensively he doesn’t do all those things.”

In an Esquire interview published three months later, he added that Jeter “has never had to lead.”

It was like a line drive to Jeter’s heart. And A-Rod knew almost instantly he made a major mistake.

He drove 90 minutes from the Rangers training camp in Port Charlotte, Fla., to Jeter’s home in Tampa to apologize. An emotional A-Rod waited outside Jeter’s home, while Jeter, fully aware that A-Rod was there, lingered at a meal in a local nightclub.

When Jeter finally arrived home, A-Rod begged for forgiveness.

But Jeter was the kind of guy who needed only one strike to remove you from his life, and A-Rod already had just committed two.

“If you do something to hurt [Jeter], that’s it, you’re done,” Mike Borzello, a bullpen catcher close with Jeter, told the author. “You had your chance.”

Jeter got a measure of revenge at the 2001 All-Star Game, when a smitten Rodriguez introduced him to Latin songstress Joy Enriquez. Jeter wasted no time — the singer and the shortstop began dating.

So it was understandable that Jeter was less than thrilled when the Yankees traded for his foe before the 2004 season.

Clubhouse sniping came quickly. An unnamed player described the new arrival as “very phony,” the book says. A-Rod would ignore stadium employees and seemed oblivious to fans, even sick young kids, who clamored for his autograph. Jeter, who prized poise and selflessness, dismissed A-Rod and his diva-like behavior.

And when fans and rival players criticized A-Rod, Jeter deferred instead of defending his teammate.

General Manager Brian Cashman noticed this and asked Jeter to “fake it” with A-Rod.

“You’ve got to lead them all, the ones you like and the ones you don’t,” he told him. He asked him to appeal to Yankees fans on A-Rod’s behalf.

“I can’t tell the fans what to do,” Jeter countered.

A-Rod’s obsession with Jeter continued, the book says. He constantly asked players and team officials about Jeter — down to which charity he was currently supporting.

It all came to a head during a Yankees loss in August 2006 to Baltimore.

An easy pop-up hung in the air between A-Rod and Jeter. Both players closed in and Jeter bumped into A-Rod, knocking the ball out of his glove. Jeter shot A-Rod a withering look.

The gesture did not go unnoticed. Cashman pulled Jeter aside and ordered him to knock it off.

“Listen, this has to stop,” Cashman said. “Everybody in the press box, every team official, everyone watching, they saw you look at the ball on the ground and look at him with disgust like you were saying, ‘That’s your mess, you clean it up.’ ”

A-Rod also felt betrayed by manager Joe Torre, who players said added fuel to the fiery feud.

“He would never call Jeter on anything, but he’d have no problem doing it to Alex,” one player told the author.

Things didn’t gel until A-Rod hit rock bottom in 2009. He had been “emasculated,” outed as a steroid user and an unfaithful husband the year before.

Jeter began engaging in small talk with the third baseman in the clubhouse and he and girlfriend Minka Kelly even dined with A-Rod and his then-flame Kate Hudson, where they all seemed to enjoy each other’s company, the author says.

In the 2008 off-season, Cashman set his sights on signing prized free agent CC Sabathia, the Milwaukee Brewers’ Cy Young Award winner.

“CC’s main concern was our clubhouse, and how people got along,” Cashman told the author. “I told him the truth. ‘Yeah, we are broken. One reason we’re committing [$161 million] to you is you’re a team builder. We need somebody to bring us together.’ ”

The Yankees ponied up extra cash — the most expensive contract for a pitcher to date — to bring the clubhouse Band-Aid to the roster.

Meanwhile, time — and most importantly wins — softened the rift between the two players.

“Derek understands Alex’s positives and negatives,” said Buck Showalter, who managed both Jeter and Rodriguez early in their careers. “He’s come to understand the way Alex is.”

scahalan@nypost.com