The Yankees haven't won consecutive games since an Aug. 15-17 sweep of the Rangers, which may be the most distressing statistic to come out of their swoon. Meanwhile, the Orioles topped the Rays 9-2, sliding back to a tie for first place in the division.
"We need to play well down the stretch if we want to accomplish what we want to accomplish," manager Joe Girardi said. "We haven't been able to get on a roll and we haven't been consistent."
The Yankees fell in the home half of the ninth, creating some excitement for a crowd rooting on a Red Sox team playing out the September string, but they had plenty of chances earlier as Jon Lester walked a career-high seven batters in a wild effort.
"We have to try to find ways to score more runs," Jeter said. "You tip your cap to the pitcher sometimes, too, but he didn't have a lot of control, so we had a lot of opportunities we let get away from us."
Boston pushed across the winning run against David Robertson in his second inning of relief work, as Yankees killer Pedro Ciriaco improved to an unfathomable 17-for-35 against New York with a single to open the ninth.
Mike Aviles followed with an infield hit that Jeter had no options on, and Ellsbury punched a ground ball into right field, scoring Ciriaco ahead of Ichiro Suzuki's throw for Boston's third walk-off win of the year.
"It's tough, it really is," Robertson said. "It seems like a lot of those balls that didn't sneak through last year are sneaking through this year. I'm having a rough go of it right now."
The loss came to a Red Sox club coming off an address from manager Bobby Valentine, urging them to keep their heads up and play spoiler despite a disappointing year.
"I told the guys before the game that the fans are still pulling for us and they want to see us play well," Valentine said. "The season's not over and we owe it to them, to the organization, to give it everything we have. And I think we did tonight."
The Yankees took a first-inning lead as Robinson Cano's groundout knocked in Jeter, but Lester avoided further trouble after opening the game with runners at second and third and none out, one of the chances that would loom large in the end.
Jeter gave the Yankees the lead in the sixth, flaring a two-run ground-rule double to right field, but that was the only hit with runners in scoring position they'd produce against Lester and three Boston relievers, finishing 1-for-12.
"You'd like to think it'd get something going, but they made some pitches when they needed to," Jeter said.
Starter Hiroki Kuroda allowed three runs on eight hits over his 6 1/3 innings of work, giving back a pair of leads and accepting a no-decision.
"Compared to those days that I have all my stuff, I just didn't have all my stuff today," Kuroda said through an interpreter. "I tried to be tough out there, minimize the damage and try to stay tough."
The Red Sox struck for two runs in the third inning, as Ciriaco stroked a leadoff double and scored on an Ellsbury single. Dustin Pedroia also added a RBI single to give Boston the lead.
"He's been killing us this year," Jeter said of Ciriaco. "He seems like he enjoys playing us."
Kuroda also lost a one-run advantage in the sixth, serving up Pedroia's line-drive homer that just cleared the Green Monster in left field.
"You talk about shutdown [innings]," Girardi said. "That's what you preach from Day 1, and we weren't able to do it. [Kuroda] gets behind Pedroia and a fastball leaks back across the middle of the plate, and he hits a homer."
Boone Logan neglected to cover first base on a seventh-inning play, loading the bases with one out, but Joba Chamberlain bailed Logan out by inducing two quick outs.
"It's probably one of the most embarrassing things a pitcher can do," said Logan, though both he and Girardi didn't think he would have beaten Ellsbury to the bag anyway.
Nick Swisher laced a one-out single in the ninth against closer Andrew Bailey, but pinch-runner Eduardo Nunez was thrown out stealing and Alex Rodriguez fanned, wiping out the Yankees' chance to put a pair of wins back-to-back.
"We've kind of got ourselves into a 22-game race right now," Swisher said. "It's going to be a lot of fun. I'm excited for it. We've put ourselves in this position. We control our own destiny."