NEW YORK — Kevin Youkilis hit a tying three-run homer, David Ortiz had a go-ahead drive and the Boston Red Sox completed a sweep of the reeling New York Yankees with a 7-5 victory Sunday night to reach .500 for the first time this season.

Jon Lester (5-1) shrugged off a slow start to beat New York again and Jarrod Saltalamacchia hit his first homer with Boston as the Red Sox swept a three-game series in the Bronx for the first time since April 2004.

Heavily favored to win the AL East, the Red Sox opened the season 0-6 but finally evened their record (20-20) on their fourth try.

Despite jumping out to a 4-1 lead, the Yankees matched their longest losing streak since May 2009 by losing their fifth straight — all at home — a slump plagued by shaky defense, a lack of big hits — and a huge dose of turmoil.

Jorge Posada was in the middle of the uproar Saturday, pulling himself from the lineup about an hour before gametime, saying he needed a day to clear his head after being dropped to ninth in the batting order.

The struggling designated hitter apologized Sunday to manager Joe Girardi and general manager Brian Cashman for his actions on what he characterized as “a bad day.” The Yankees said they will not punish the five-time All-Star and consider the matter closed.

Cashman said it was time to move on and focus on the Red Sox and righting the Yankees, losers of nine of 12.

Posada entered as a pinch-hitter to open the eighth and received a sustained ovation. He walked but Daniel Bard retired the next three batters.

Jonathan Papelbon pitched the ninth for his seventh save.

Alex Rodriguez let a ball roll through his legs in the seventh inning for an error, allowing the Red Sox to take a 6-4 lead — an insurance run they would need in the bottom half. Carl Crawford failed to cleanly pick up Rodriguez’s double to left field for an error, which gave Curtis Granderson time to score from first.

But Nick Swisher struck out against Bard with runners on first and second to drop to 0 for 17 with runners in scoring position and two outs this year. Since May 2, the Yankees are 21 for 95 (.221) with runners in scoring position overall.

Even though Posada was not in the starting lineup because he was 0 for 24 against lefthanders this season, the Bleacher Creatures finished their roll call with chants of “Jorge!” that elicited a cheer from the crowd of 46,945. Posada gave a wave from the dugout.

Posada was first to the top of the dugout steps to greet designated hitter Andruw Jones, who hammered a pitch from Lester deep into the left-field seats leading off the second for a 2-1 lead.

Granderson connected for a two-run shot four batters later, the first homer Lester has allowed against a lefty batter this season.

But Youkilis spoiled the good vibes at Yankee Stadium with a three-run shot off Freddy Garcia (2-3) in the third and Otiz connected in the fifth to make it 5-4. Ortiz was a triple shy of the cycle.

Lester settled after a rocky start, giving up just one hit and striking out five after the second inning.

He walked two in the sixth between strikeouts but got Brett Gardner to pop up to first for the third out.

Lester struck out seven and walked four in six innings to win his fifth straight decision this year and improve to 7-1 against the Yankees.

The Red Sox loaded the bases with none out in the second but only scored one run off Garcia, on Jed Lowrie’s sacrifice fly.

Saltalamacchia homered off Joba Chamberlain in the eighth for his first homer since Aug. 2, 2009, for Texas against Seattle.

Saturday night, Boston’s Josh Beckett shut down the for the second time this season and Adrian Gonzalez homered for the fourth consecutive game, sending the Red Sox to 6-0 victory.

“That’s probably the best cutter I’ve seen him have in a while. Changeup — he used all his pitches,” Boston manager Terry Francona said. “We have a lot of confidence in him. We always have. He worked hard and said last year he was going to come back with a vengeance, and I think he has.”

NOTES: Adrian Gonzalez’s streak of homering in four straight games — five homers total — came to an end. … Garcia has not allowed a grand slam in his career, 1,966 1-3 innings. … Josh Beckett turned 31 Sunday. … Marco Scutaro (strained oblique) on the DL since May 8 will rejoin Red Sox in Boston on Monday to continue his rehab. He was not with the team during the five-game road trip. … Joe DiMaggio began his 56-game hitting streak on May 15, 1941, 70 years ago. … Steve Martin and Mike Myers sat in front row behind home plate.