The New York Yankees battered Pedro Martinez, chasing Boston out of town with their second rout in a row.

Gary Sheffield, Derek Jeter, and Jorge Posada home red off an ineffective Martinez, and Mike Mussina gave the resilient Yankees another excellent outing yesterday as New York opened a 4 1 /2-game lead in the AL East with an 11-1 victory.

“They put us in the rearview mirror a little bit,” Red Sox manager Terry Francona said.

Alex Rodriguez also connected in the second consecutive offensive outburst by the Yankees, who outscored their longtime rivals 25-5 the past two days after a deflating loss Friday night, when star closer Mariano Rivera blew a ninth-inning lead.

The Yankees’ hitters lit up Derek Lowe and Martinez, and the pitchers shut down the highest-scoring team in the major leagues with a pair of dominating performances.

After taking two of three in the series, the Yankees have some breathing room – their largest lead over Boston since before the games of August 31. New York has 13 games remaining as it closes in on its seventh straight division title, while the Red Sox play 14 more.

“We just feel like we’re the best team in baseball,” Sheffield said.

The teams play another three-game set next weekend at Fenway Park. By then, the Red Sox might be too far back to catch New York, though they still have a 5 1 /2-game lead over Anaheim in the wild-card race.

“If we get to the playoffs, believe me, we’re not going to be the ones who are scared,” Martinez said.

Boston lost its first series since dropping two of three August 13-15 against the White Sox. The Red Sox also lost consecutive games for only the second time since August 7.

Serenaded with a haunting chant of “Pe-dro, Pe-dro,” Martinez (16-7) lasted only five-plus innings and allowed eight runs, matching a season worst. He had pitched at least six innings in 18 straight starts since June 2 at Anaheim.

The Boston ace, who couldn’t hold a three-run lead in the eighth inning of Game 7 in the 2003 AL championship series at Yankee Stadium, has dropped consecutive starts for the first time since June 2002.

Featuring a nasty knuckle-curve, Mussina (12-9) struck out eight, including Jason Varitek three times. The right-hander allowed seven hits in seven innings, winning his third straight start since losing a career-worst five straight decisions. Mussina has a 1.20 ERA in his last four outings spanning 30 innings.

Boston slugger Manny Ramirez was hitless in eight at-bats during the series. Varitek went 0-for-10 with eight strikeouts.

The Yankees came out swinging against Martinez, who fell behind 2-0 after four pitches. Rodriguez singled up the middle with one out in the first, and Sheffield lofted a high fastball into the left-field corner for his 35th homer of the season.

Right after he left the game, Sheffield got two more cortisone shots in his ailing left shoulder.

With his parents cheering him on in the stands, Jeter connected on Martinez’s first pitch in the third, making it 3-0. Boston scored in the fifth on Orlando Cabrera’s bloop double and Johnny Damon’s RBI infield single, but the Yankees broke it open with a five-run sixth.