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 9 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, giving 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.

Even though Posada was not in the starting lineup because he was 0 for 24 against left-handers 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.

Yankees spokesman Jason Zillo said Cashman informed owners Hal and Hank Steinbrenner, along with club president Randy Levine, about Posada’s apologies, and the team considers the matter closed. Zillo said the Yankees will not take any disciplinary action.

“We had a nice conversation. We talked about being emotional and going through struggles and what defines who you are. He apologized and said, ‘I had a bad day,’ and I said, ‘I have had bad days, too,”‘ Girardi said. “‘I know it’s hard to struggle, but you’re going to get through this.”‘

On the field, Posada hugged Alex Rodriguez and chatted with other teammates during batting practice. Yankees captain Derek Jeter, one of Posada’s best friends, said the issue was resolved and he saw nothing wrong with what his pal did Saturday.

“It’s not the first time that someone has come out of the lineup,” Jeter said. “If you need a day, you need a day. … If I thought he did something wrong, I’d be the first to tell him.”

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 inning 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 inning and Ortiz connected in the fifth to make it 5-4. Ortiz was a triple shy of the cycle.

Lester settled down 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.

NOTES: Marco Scutaro (strained oblique) on the DL since May 8, will rejoin the Red Sox in Boston today to continue his rehab. He was not with the team during the five-game trip.