BOSTON (AP) - New York Yankees manager Joe Girardi found little to get excited about after Mark Teixeira's solo homer in the sixth inning.
After all, the Yankees still trailed by eight runs.
"You're down 9-0 and Tex hits what looks like an innocent home run. Then we come back with back-to-back seven-run innings," Girardi said after New York rallied to beat Boston 15-9. "I don't think I've ever been a part of that."
Nick Swisher hit a grand slam in the seventh to help the Yankees erase a 9-0 deficit, then he added a two-run double in the eighth to give them the lead. The comeback matched the franchise's largest deficit overcome in a win, done five times.
Teixeira had six RBIs, homering from both sides of the plate for the 13th time in his career.
"That was pretty cool," Teixeira said. "I've played a lot of games, and that may be the most fun regular-season game I've ever been a part of."
A day after Red Sox starter Clay Buchholz gave up five homers and the Yankees spoiled Fenway Park's 100th anniversary party, Boston chased New York starter Freddy Garcia after 1 2-3 innings and opened a nine-run lead through five.
But Teixeira homered twice, the second a three-run shot in the seven-run seventh that cut the deficit to 9-8. Swisher, who also had six RBIs, hit a two-run double off the center field wall in the eighth to make it 10-9.
The Yankees added five more as Red Sox manager Bobby Valentine used three pitchers - including closer Alfredo Aceves (0-1), who allowed five runs and failed to record an out - to get out of the inning.
Rafael Soriano (2-0) pitched one inning of scoreless relief.
"I don't like to lose. I don't know anybody who does," Boston shortstop Mike Aviles said. "This wasn't fun at all. I don't want to see it if it gets any worse."
It was Boston's second straight loss to the rival Yankees, each of them heart-breaking in its own way. Friday's 6-2 loss cast a pall over the feel-good 100th anniversary celebration, but the sequel on Saturday exposed the bullpen and had the hometown fans booing Valentine just 14 games into his Red Sox career.
Valentine tipped his capped to the fans as they booed him when he walked back from making a pitching change in the eighth.
"I've been booed in a couple of countries; a few different stadiums. I don't want to be booed," said Valentine, who was asked if he had any regrets about leaving broadcasting to take the Red Sox job. "If they said it was only going to be for the good days, I probably wouldn't have come. The challenges are great."
Felix Doubront held New York scoreless on three hits until Teixeira hit a solo homer with two outs in the sixth. By that time, Boston led 9-0 thanks in part to a two-run homer by Cody Ross and RBI doubles from Adrian Gonzalez and David Ortiz.
Ortiz had four hits and a walk, and Aviles drove in a pair of runs for Boston, which has now won just 11 of 41 games dating back to Sept. 1, 2011.
"I think we've hit bottom," Valentine said. "If this isn't bottom, we need to find some new ends of the earth."
The Yankees improved to 9-3 since they were swept in the season-opening series by the Tampa Bay Rays.
The Red Sox scored two in the first on back-to-back RBI doubles from Ortiz and Gonzalez, added three in the second to chase Garcia and then made it 7-0 in the third. Ross homered in the fifth to give Boston a 9-0 lead.
Teixeira hit a solo homer in the sixth, then the Yankees made it a one run game with Swisher's grand slam and a three-run shot by Teixeira.
Swisher put the Yankees up 10-9 with a drive off the center field wall. There was still nobody out in the inning when Teixeira added a two-run double; Russell Martin added a two-run, two-out double and Derek Jeter was given an RBI single that made it 15-9 when shortstop Aviles slipped and fell on his rear end as he went to throw to first.
NOTES: The Yankees shut down RHP Michael Pineda when he felt weakness in his shoulder after 15 pitches during an extended spring training game in Tampa. ... Girardi said LHP Andy Pettitte would probably make his next start in Double-A Trenton and be limited to 80-85 pitches. ... Red Sox 3B Kevin Youkilis left the game in the fourth inning with a bruise on his left quadriceps. ... Ortiz is 17 for 32 on the homestand with 10 RBIs. ... The most runs the Yankees have scored after the sixth inning was 16, against the Red Sox on June 19, 2000.