But things went awry as Pettitte's strong afternoon quickly came unhinged and the Yankees' normally-sound bullpen faltered. The Athletics took advantage, batting around for six runs and holding on for a 6-4 victory that snapped New York's eight-game winning streak.
"It's a frustrating game," Pettitte said. "We've been playing so well, and to be throwing the ball like I did and to feel as good as I did, it's pretty amazing to let it get away like that."
The troublesome frame began with Pettitte clinging to a one-run lead, having allowed a leadoff double to Scott Hairston and a walk to Nomar Garciaparra. That blip interrupted a six-inning sequence that had seen Pettitte limit the A's to two hits with seven strikeouts.
Pettitte got Jack Cust to fly out to center field for the first out, and Girardi trotted to the mound, glancing at Alfredo Aceves warming up in the right-field bullpen. The Yankees needed a double play, and Pettitte said he could produce it.
"I just wanted to make sure that he felt good," Girardi said. "He said he felt good. I liked the way he was throwing the ball. He had gotten a lot of ground balls and I liked our chances."
Rajai Davis made the Yankees pay, stroking a game-tying bullet past Pettitte into center field. Bobby Crosby laid down a perfect bunt up the third-base line for a single that chased Pettitte.
After recording the second out on a Mark Ellis popout, Aceves couldn't get an 0-2 pitch to backup catcher Landon Powell in enough and surrendered a two-run single that gave Oakland its first lead of the afternoon, one it would not relinquish.
"Sometimes when you give up a hit right there, you feel like that's a big blow, especially after he got the popup," Pettitte said. "You lose your focus a little bit. He's been great and he'll continue to be great."
Aceves has been one of the Yankees' more reliable bullpen arms, but this time, he could not limit the damage. He also permitted a RBI single to Adam Kennedy -- the run charged to Pettitte -- and a two-run double to Orlando Cabrera before leaving the field showered with boos.
"It was hard, man," Aceves said. "I wanted to do the job."
Oakland sent 10 men to the plate in the inning, and Pettitte's final line tagged him with four runs allowed on five hits over 6 1/3 innings. He walked one.
"We just weren't able to close out that [seventh] inning," Girardi said. "The numbers are probably going to look a lot worse than what he pitched. I thought he pitched a really good game. Our bullpen has been so great, and today, we just weren't able to get it done."
"He was very tough," agreed A's manager Bob Geren. "He had good control of the outside of the plate. We were fortunate to get some runs off of him."
Pettitte lost his third straight decision, despite retiring the first 10 batters in order and leaving with the bases loaded and the score tied 1-1. He wasn't in the mood to accept platitudes.
"Losing games is sickening," Pettitte said. "I'm not looking for steps forward. I'd rather give up six runs in six innings and feel good about it. I don't need positive outings right now at this stage in my career, that's for sure. I'm looking for wins."
Through 5 1/2 frames, the game featured a compelling duel of shutouts between Pettitte and A's left-hander Gio Gonzalez.
The Yankees scored first, as Brett Gardner ripped a sixth-inning RBI triple up the gap in right-center to chase Derek Jeter home. But Gonzalez evaded further damage and the Yankees found the sneaky left-hander and his 9.33 ERA entering the game perplexing.
"We were saying on the bench, we didn't know how he could have an ERA like that," Jeter said. "He was outstanding. We couldn't get anything going. We got two hits off him, so he pitched well."
But even after Oakland sent 10 men to the plate in the seventh, the Yankees wouldn't go quietly, putting up three runs in the eighth inning against A's setup man Michael Wuertz.
"I loved the way our guys came back today," Girardi said. "It's unfortunate we lost that game."
Jeter added a two-run homer, his 11th -- tying his mark from all of last season -- and Mark Teixeira connected for a long solo blast, his team-leading 25th, cutting the deficit to two runs.
They still had a chance in the ninth inning against Andrew Bailey, as Melky Cabrera worked a leadoff walk and Johnny Damon also produced a free pass, bringing Jorge Posada to the plate as the potential winning run.
"I was thinking that Jorgie was going to hit a three-run homer," Girardi said. "He hit it hard."
But the ball didn't clear the wall, not even close, skidding into Ellis' glove at second base for a double play. Jeter flew out to center field to end the game, just the Yankees' sixth loss in their past 27 games overall.
"I'm thinking, 'One swing of the bat and this game is ours,'" Nick Swisher said. "Either way, it was a great run for us. It's over now, and we might as well start it up tomorrow."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.