A.J. Burnett #34 of the New York Yankees salutes the...

A.J. Burnett #34 of the New York Yankees salutes the crowd as he leaves the game in the eighth inning against the Milwaukee Brewers at Yankee Stadium. (June 29, 2011) Credit: Jim McIsaac

Apparently, the key to understanding A.J. Burnett's impressive transformation really is simple.

With the help of his burgeoning confidence and a redefined changeup, the Yankees starter put together another solid outing Wednesday night, allowing just two runs in seven innings to seal a 5-2 victory over the Brewers at the Stadium.

It was the fourth straight win and 14 out of 18 for the Yankees (47-31), who took a 21/2-game lead over the Red Sox in the American League East -- their largest since May 2.

Jorge Posada and Russell Martin each went deep, bringing the Yankees' major league- leading total to 115. The Yankees have six players with double-digits homers, the most of any club.

While Martin's three-run blast, which snapped a 68 at-bat homerless streak, was never in doubt, Posada needed the help of instant replay.

With his mother in the crowd, Posada trotted slowly around first base after ripping a slider from reliever Tim Dillard to rightfield in the sixth. There was no doubt in his mind that he had just collected his ninth home run -- that is until, in a confusing blur of events, rightfielder Corey Hart wound up with the ball and threw Posada out halfway between first and second base. The crowd groaned, frustrated by an inexplicably blown call.

"They told me to get on first base and wait for whatever happens," said Posada, who is hitting .404 (21-for-52) since June 5.

His home run hit off the top of the wall and ricocheted off the hands of a fan seated in the first row. Television replays showed the fan shouting "It hit me!" during the review. After several minutes, the umpiring crew reversed the call and Posada continued his jog around the bases.

While Shaun Marcum (four runs in five innings) struggled, Burnett (8-6, 4.05 ERA) gave the Yankees distance, lasting seven innings for the third time this month. The Brewers (44-37) pulled to within 4-2 in the sixth on a fielder's choice with two outs. But Burnett used his curveball to induce an inning-ending groundout.

"I threw some changeups tonight in counts where they were big pitches . . . and normally in the past it was all fastball, fastball, fastball," said Burnett, who received a rousing ovation from the crowd of 46,450 when he exited in the eighth. "In the past I let a lot bother me, and errors are going to happen and hits are going to happen. Me going out there one pitch at a time has been the difference."

Robinson Cano led off the four-run fourth with a triple that was misplayed by centerfielder Nyjer Morgan. Morgan sprinted toward the warning track, but crashed violently into the padding and fell to the dirt. Nick Swisher singled to shallow right, scoring Cano and tying it at 1. Posada followed with a hard-hit single off the rightfield wall, advancing Swisher to third before Martin belted his 10th homer over the leftfield wall.

It was his first home run since May 24 against Toronto's Ricky Romero.

The Brewers threatened in the eighth, after Rickie Weeks reached on another error by Eduardo Nuñez. Burnett's replacement, David Robertson, gave up a two-out single to Prince Fielder before striking out Hart looking to end the inning. Mariano Rivera made his 1,011th appearance (12th all-time) in the ninth and earned his 21st save with a 1-2-3 inning.

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