Not only did he throw seven scoreless innings, he matched a personal best with nine strikeouts while walking just one.
"This is what makes you better," Chamberlain said. "This is why you play the game. You understand it's going to be a tough game and this is the way it's going to be. You can't break. Josh is an unbelievable pitcher. He battles and claws, and we got that one break. Jason hit that ball right where it needed to be."
With no margin for error and protecting a one-run lead, Chamberlain retired the final 10 batters he faced.
"This is how you get better," Chamberlain added. "This is the way you want it to be, and this is the way it's going to be for the rest of the year."
Chamberlain is quickly validating management's decision to move him from the bullpen to the rotation with arguably his finest outing in pinstripes.
"He was outstanding," said Yankees skipper Joe Girardi. "He matched Beckett inning for inning, and it was a great pitched game on both sides. You have seven strong innings and only 100 pitches. He was great."
Chamberlain was pulled after the seventh, throwing 103 pitches, 69 for strikes.
"He seems to get stronger as the game goes on," Girardi said. "The first two innings, he didn't really find his groove, but after that, he seemed to really get going."
Spectacular defense helped Chamberlain through the early innings. In the second, Melky Cabrera made a diving stab of J.D. Drew's sinking liner in center. That was followed by Robinson Cano backhanding a tricky grounder off the bat of Jed Lowrie, flipped to Derek Jeter and starting an inning-ending double play.
"That was unbelievable," Girardi said of Cano's gem. "The double play and the catch by Melky, just great defense. Probably saved a run those couple of plays."
And there was another Chamberlain moment with Boston first baseman Kevin Youkilis. The righty buzzed Youkilis up and in with a fastball in the seventh inning. Both teams were warned after the pitch, which hit Youkilis' bat for a foul ball.
"Nobody wants the ball right there," said Chamberlain. "Nobody wants the ball in at 90 [mph], whatever it was. But at the end of the day, it's 1-0, and I'm trying to get a win and it's what you have to do. It's a 2-0 count and the game's 1-0, you think I want to lose the lead and put the lead runner on with those guys behind him? No shot."
Yankees closer Mariano Rivera converted his 26th straight save by recording the final five outs, including working out of a first-and-second jam in the eighth. Rivera struck out Jacoby Ellsbury before getting Dustin Pedroia on a comebacker to the mound.
The victory extended New York's winning streak to seven games and drew the Yankees to within two of their archrival in the AL East, while also remaining three back of the Rays.
Alex Rodriguez and Bobby Abreu each had two hits to lead New York, starting a two-out rally in the third inning. After Abreu and Rodriguez singled off Beckett, Giambi singled to short with the infield shift on, allowing Abreu to cross the plate.
"He was tough on me tonight," Giambi said of Beckett. "He was throwing breaking balls down and away and fastballs in. He had a good game plan on me tonight, and when I came up first and third, it definitely helps when you have runners that spread out the shift a little bit. I just stayed inside the ball."
Beckett was the hard-luck loser, allowing nine hits and just one run while striking out six and walking one in his seven innings, while David Ortiz singled in four at-bats in his return from a eight-week absence due to a sore left wrist.
"Jason had that swinging bunt, and we were fortunate to get that run," Jeter said. "Any time you face a pitcher like Beckett, you realize you're not going to score too many.
"Every game is big at this point, and today, Joba deserves all the credit. Obviously, our bullpen did a good job, but we have to take every game like we have to win, regardless of who we're playing, whether we're at home or on the road. We don't have the luxury of taking any days off."