Updated

Another game, another loss, and another step closer toward an October at home for the Red Sox.

A.J. Burnett shut down Boston for 7 2/3 innings and Jorge Posada hit a two-run homer, leading the Yankees to a 6-2 victory over the Red Sox in the opener of a doubleheader.

The loss continued Boston's September slide and further jeopardized its wild card lead. The Red Sox, now 5-18 during the month, entered Sunday with a 1 1/2 game edge over the Rays.

But Tampa Bay beat Toronto, and if Boston loses Sunday's second game, its lead will be gone -- a stunning fact considering the Red Sox entered September with a 1 1/2 game lead in the division.

"Offensively we have to step up," Red Sox second baseman Dustin Pedroia, "We'll figure it out."

Burnett (11-11) played a big part in dealing the Red Sox the loss in the opener, giving up two solo homers to Jacoby Ellsbury. He allowed only five total hits, walked two and struck out six.

It was the right-hander's first victory against Boston in three seasons as a member of the Yankees. He had been 0-4 in nine previous starts.

Derek Jeter helped support Burnett by going 3-for-4 with a run-scoring double, and scored twice as New York won for the sixth time in seven games.

Boston starter Tim Wakefield (7-8) gave up five runs -- three earned -- in four-plus laborious innings. The knuckleballer allowed five hits and walked five.

"We didn't jump on him. We had two bunt hits," Jeter said of Wakefield. "I wouldn't say we jumped on him, we were just fortunate."

The Yankees jumped out to the lead in the first inning. Brett Gardner led off with a single, stole second and moved to third on Jeter's bunt single to third. Then, catcher Jarrod Saltalamacchia's error allowed Gardner to race home as Jeter swiped second.

Later, a passed ball and wild pitch allowed Jeter to take third and score, giving the Yankees a 2-0 lead.

New York doubled its advantage with one swing in the third. Wakefield walked Alex Rodriguez on five pitches before getting into a 1-1 count against Posada. His third pitch to the Yankees designated hitter was a knuckleball that hung directly over the plate, and Posada hammered it to the second deck in right field.

Burnett made the lead stand by facing the minimum through three innings.

Ellsbury began the fourth with his first home run of the game, but the Yankees got that run back in the fifth. Jeter singled and moved to second on an error by Carl Crawford, then scored on a base hit by Rodriguez.

Ellsbury went deep again in the sixth, but again the Yankees responded. Jeter's ground-rule double in the home half scored Brandon Laird, who had singled.

Burnett and the Yankees' bullpen took care of the rest. He faced the minimum in the seventh and recorded two outs in the eighth, which David Robertson finished. Robertson pitched the ninth to secure the win.

Game Notes

Ellsbury had his third multi-homer game of his career, and second of the season (July 20 vs. Baltimore)...Boston fell to 11-6 vs. the Yankees this year.