The defeat dropped the Yankees into a first-place tie with the surging Orioles and created the type of good feeling that has been glaringly absent around the Red Sox in recent weeks.
"I told the guys before the game that the fans are still pulling for us and they want to see us play well," said Valentine. "The season's not over and we owe it to them, to the organization, to give it everything we had, and I think we did tonight."
Perhaps playing the role of spoiler can help to rejuvenate the Red Sox, who notched just their second win in the last 12 games.
Ellsbury capped his monster birthday (4-for-5) by giving the Red Sox just their third walk-off hit of 2012, and first since July 19.
"We told ourselves, 'Keep on competing.' The fans were great tonight," Ellsbury said. "We want to keep on putting on a show for them through the rest of the season."
It was fitting that Ciriaco started the winning rally. A Yankees killer all season, he slapped a one-out single to left against David Robertson. Ciriaco went 2-for-3 to improve to 17-for-35 against New York. Mike Aviles kept the rally going with a single deep into the hole that shortstop Derek Jeter didn't have a play on.
"Ciri and Mike did a good job of getting [us] in scoring position," said Ellsbury. "I knew if I hit something to the outfield, Ciri is going to score with his speed. Just trying to drive something, hit something on the nose, and allow Ciri to use his speed."
The walk-off celebration was the first moment of pure joy for the 64-78 Red Sox in weeks.
"It was a change," said Cody Ross. "It seems like the past few weeks have been not very good atmosphere-wise. Losing doesn't help. Tonight, the way it happened -- Jacoby has a huge game. [Dustin] Pedroia with another big game. [Jon] Lester battled and our bullpen came in and did a great job. Just a fun game to be a part of."
Rookie catcher Ryan Lavarnway helped put the Red Sox in position to win in the top of the ninth, when he cut down pinch-runner Eduardo Nunez on a stolen-base attempt.
The bullpen also came up big. Junichi Tazawa went 1 2/3 innings, striking out three. Craig Breslow worked a clean eighth. Closer Andrew Bailey came on for the ninth to earn his first win for the Red Sox.
"That was a big inning, going into the bottom of the ninth and trying to get a walk-off win," said Bailey. "That's fun baseball. Today was probably the most fun we've had in a while. I'm always going to be excited out there. I was excited to get out of that inning. Ryan made a great throw to get that guy at second. That was huge for us."
Playing the role of spoilers isn't ideal, but it gives the Red Sox something to compete for.
"I don't want to be fodder on any of their bulletin boards, but we're equal opportunity and we're going to go out and we're not going to lay down," Lavarnway said. "We're here to play, and we're here to win. Nothing would be more awesome than knocking these guys out of the playoffs. Then we get to play the Rays and knock them out. Then play the Orioles and [try to] knock them out, too."
Lester didn't have anything close to his best command, issuing a career-high seven walks, but he made up for it with grit. The lefty battled hard in this one, giving up five hits and three runs over 5 1/3 innings. He threw 102 pitches, just 55 for strikes.
There was also a milestone, as Lester notched career strikeout No. 1,044, passing Bruce Hurst for the team record by southpaws.
For Lester, the first inning was a grind. He walked three but allowed just one run, which came on a fielder's-choice groundout by Robinson Cano.
"First pitch on, I was pitching uphill the whole night," Lester said. "I wasn't giving myself a chance. I wasn't in good pitchers' counts. I just didn't have a feel for anything. It was one of those nights where I had to battle through it. I tried to keep my team in it as best as I could and go as deep as I could. Taz did a great job coming in and getting us out of that inning. That was a big inning for us, and obviously stringing something together in the ninth was good."
In the third, there were some more command issues for Lester. He opened the inning by walking Alex Rodriguez and Cano. Lester was openly frustrated at home-plate umpire Chad Fairchild. At that point, Valentine came out to the mound and emphatically told Lester to worry about the hitter, not the umpire. Lester dug down, getting two strikeouts and a groundout to get out of the inning unscathed.
"He didn't have his best command today, but he battled," Lavarnway said. "[It] wasn't the easiest day. That's what he's done, time in and time out, every time I go out there and I catch him, whether he has his best stuff or not, he's battling. He kept us in that game when it could have gotten away from us early."
With Lester at 99 pitches and Boston clinging to a 2-1 edge in the sixth, Valentine came out for a visit. Derek Jeter worked the count to 3-2 on Lester and then fisted a two-run ground-rule double down the right-field line, giving New York a 3-2 lead.
It took just one swing for the Red Sox to tie it, and Pedroia provided it in the bottom of the sixth, walloping one over the Monster to make it a 3-3 game.
Ultimately, Ellsbury gave the Red Sox the hit they needed.
"They have a lot of pride," Jeter said. "They've got guys on the team that have pride in how you play the game, so I'm sure they would like to do that. When you're competing, you want to win. I don't care where you are in the standings -- especially when it's Red Sox-Yankees. Guys want to play well.