Two batters later, Donaldson touched home on a Cliff Pennington homer.
"That's one run, and we lost by one run," Girardi said. "To me, I always say that that's the hardest play for me to see -- the bang-bang play -- but I thought he was out by about a step. I didn't even think it was close. [Vanover] thought he beat it. I never saw the replay, but I heard the reaction of the crowd, and that usually tells you what the replay says. It's unfortunate."
The Yankees needed length from starter Hiroki Kuroda after their wins took 10 innings Friday and 14 innings Saturday, but when the right-hander departed with a man on in the sixth inning Sunday, they had neither relief for their bullpen nor a lead.
Pennington's home run -- on a slider Kuroda said he missed up and over the plate -- gave the A's a 3-0 lead, and although New York scored four runs in the fourth to go ahead by a run, the advantage was brief, with Kuroda surrendering two more runs the next two innings.
"He's keeping us in the game, that's the bottom line," Girardi said. "We had some chances, we just weren't able to come through."
The Yankees' most consistent starter struggled from the outset, surrendering a single to Stephen Drew to lead off the game, then allowing him to score on a wild pitch. Kuroda's 5 2/3 innings marked the first time since July 6 in Boston that he did not complete at least six innings, as he routinely pitched into the seventh and beyond before September hit.
Kuroda's September ERA rose to 6.75 in four starts, although the Yankees won two of those.
He threw two wild pitches and walked three batters -- the first time he walked more than two batters in a start since June 19.
"I was trying to hit those corners and was missing the plate," Kuroda said.
He did not receive any help from his defense, as one of the five runs he allowed was unearned due to an Eduardo Nunez error.
The 25-year-old, who was sent to the Minor Leagues earlier this season to work exclusively at shortstop and improve his defense, made two errors as he started in place of Derek Jeter, who insists he is OK to play the field but still has Girardi managing his workload with a bone bruise in his left ankle.
Nunez got away with one, as reliever David Phelps -- who was dressed as Princess Leia postgame -- stranded Yoenis Cespedes in the seventh, when Nunez bobbled a ground ball and allowed the Oakland rookie to reach base. But his sixth-inning throwing error proved costly, putting Donaldson on second base and setting up a Pennington single that ended Kuroda's day.
"I know I have to keep practicing my defense," Nunez said. "Everybody knows that, and I know that. I have to keep practicing and keep working to get better and play at this level."
New York had opportunities to erase the mistake, stranding nine men on base and scoring its only runs in a fourth inning that saw Nick Swisher hit a two-run homer and Raul Ibanez sneak an RBI double just inside right-field line, kicking up chalk as it disappeared in the corner.
An inning later they had two men on with one out, but Swisher struck out looking, then turned and stood inches away from Estabrook, pointing to where he thought strike 3 arrived off the plate. And Curtis Granderson struck out swinging to end the threat.
"There were some pitches that I didn't particularly like, but you can say that every day," Girardi said.
Alex Rodriguez was the first Yankee to argue an Estabrook call, lingering at home plate in the first inning after a low called third strike. It was the first of three strikeouts in an 0-for-5 day for Rodriguez, with the boos becoming increasingly volatile with each trip back to the dugout.
But he had the crowd on its feet in the ninth, when he connected with a Grant Balfour fastball that the right-field fence somehow held, part of a 1-2-3 frame that the Yankees quickly moved over, eased with the knowledge that Baltimore already lost.
"I knew he didn't get it good, but I [also] knew that he's strong enough," Balfour said. "He doesn't have to hit a ball perfect to get it out. Especially down that right-field line. It's got to be one of the shortest porches in the game."