NEW YORK - Mark Teixeira is an MVP contender. CC Sabathia is piling up wins. A.J. Burnett is throwing heat — and the occasional whipped cream pie.

This is exactly what the New York Yankees envisioned last offseason when they spent $423.5 million on three big free agents: a pinstriped juggernaut in their swanky new stadium.

With a power-packed lineup and sturdy pitching staff, the Yankees have built a comfortable cushion in the rigorous AL East by playing money ball all summer. They’ve also loosened up that buttoned-down clubhouse for some unabashed fun, thanks to a new group of offbeat characters led by Burnett and Nick Swisher.

“We knew that if we were firing on all cylinders that we would be capable of a great deal,” general manager Brian Cashman said. “So far, this team is doing that.”

And getting plenty of bang for its bucks.

New York won 10 of its first 11 series after the All-Star break and went into the final weekend of August with the best record in baseball, by 3½ games.

After losing their first eight meetings with rival Boston this year, the Yankees won six of the next seven — including a four-game sweep at home Aug. 6-9 that gave them control of the division race.

“We’ve still got to continue to do what we’re doing, because we have not accomplished anything yet,” captain Derek Jeter said. “It seems like it gets harder and harder to win.”

Of course, Jeter was talking about winning it all. Despite having the game’s highest payroll year after year, the Yankees haven’t won the World Series since 2000. Their last pennant came six years ago.

But after missing the playoffs last season, ending a streak of 13 straight appearances, New York has that championship look again.

“We’re playing with a lot of urgency and a lot of excitement and confidence,” Alex Rodriguez said.

At 35, Jeter is having one of his best years at the plate and he’s closing in on Lou Gehrig’s club record for hits (2,721).

Teixeira’s numbers took off as soon as Rodriguez returned from hip surgery May 8, providing the switch-hitting slugger with valuable protection in the middle of the order.

Jorge Posada, Hideki Matsui and Robinson Cano are enjoying resurgent seasons. Johnny Damon is nearing a career high for homers. And 39-year-old closer Mariano Rivera has been as dominant as ever, converting a career-best 32 consecutive save chances through Thursday, a streak that pushed his total to 518.

“I’ve never been on a team this impressive before,” Burnett said.

Especially dangerous in the late innings, the Yankees had compiled 40 comeback victories and 10 walk-off wins. Early in the season, Burnett began celebrating those game-ending hits by pasting teammates in the face with whipped cream pies as they were interviewed on television.

Such gleeful and juvenile revelry is far from uncommon around the majors — but it certainly was in the Yankees’ corporate clubhouse, where baseball was serious business.

“I was a little curious about it coming in, because I’ve always done it on other teams,” Burnett said, recalling the day he got the green light from Rivera. “I think everybody loves it. I think they enjoy getting a piece of the pie. I guess it’s a little way of me showing that I care. I’m pretty quiet most of the time.”

The Yankees also started holding Kangaroo Court for the first time in more than a decade, a fun ritual that features players getting fined and chided by teammates for minor transgressions such as showing up late or wearing an ugly outfit.

Rivera is the sitting judge — and Rodriguez is a favorite target.

“I think it’s terrific,” Cashman said. “This team is exceptionally close, whereas those other teams weren’t as close.”

Cashman said second-year manager Joe Girardi deserves a lot of credit for fostering that sort of environment. Starting in spring training, Girardi made camaraderie a priority with events like family day and a team trip to play billiards.

“It all starts in here. If we can’t get along in here, we ain’t going to be able to get along on the field,” Burnett said. “Everybody will tell you, you don’t have to necessarily love everybody you play with, but you’ve got to like ’em and respect ’em.

“I think everybody in here almost does love each other, though,” he added. “That’s the crazy thing about it. We’ve all been here not even a year yet and I don’t know, I’ve heard a bunch of people say that the guys that have been here are opening up more and being themselves. I wasn’t here in the past so I can’t attest to that or anything, but I think it’s awesome here. I love every day I come in here. I come to work happy every day.”

Make no mistake, this bunch still takes winning seriously. But guys like Burnett and Swisher, a chatty outfielder obtained in an offseason trade with the Chicago White Sox, have been pivotal in lightening the mood and creating a fun atmosphere.

Several Yankees think that’s made a difference on the field, especially for a team that plays under an intense microscope every night. All the key newcomers — Teixeira, Sabathia, Burnett and Swisher — have adjusted well to the pressure of playing in New York.

“They’ve embraced it. They have not been smothered by it. Instead, they’ve improved not only our play on the field but they’ve improved our chemistry in the clubhouse,” Cashman said. “Now, we have a band of brothers out there.”

There’s no feel-good vibe without winning, however, and several things have been crucial to New York’s on-field success.

Despite a handful of aging regulars, the Yankees’ key players have remained relatively healthy other than season-ending injuries to pitcher Chien-Ming Wang and outfielder Xavier Nady.

Phil Hughes’ seamless transition from starting pitcher to super setup man has provided that elusive, eighth-inning bridge to Rivera.

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And the team’s homer-friendly new ballpark has been a perfect fit for the Yankees, who have six players with at least 20 home runs for the third time in franchise history (1961, 2004).

“It seems like everybody contributes and we’re doing our job with men on base,” Cano said. “Everything is coming together. When you’re winning, it feels like something good is going to happen.”

As always, issues still linger in Yankeeland.

There are rumblings that Burnett and other pitchers don’t like throwing to Posada. Joba Chamberlain is on an innings limit and hasn’t performed well since his schedule was altered. A hobbling Rodriguez has slumped for long stretches.

Yet the Yankees, with a $201 million opening-day payroll, have been worth the hefty price thus far.

“Coming here you want to win and we expect to win, and the team’s been meshing real good,” said Sabathia, who was leading the AL in victories and innings pitched. “It’s been a lot of fun. It’s good to be on this side of it.”

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