In the end, they squeezed out a 10th-inning run on Yoenis Cespedes' infield single for a 3-2 victory to narrowly avoid a three-game sweep in Boston -- all made possible by one of Daric Barton's gutsiest plays to date in Boston's half of the inning.
The first baseman, brought in just for the 10th inning after an ankle injury to Josh Reddick forced Brandon Moss to right field, shrugged it off as something of a routine play. But it wasn't.
With Will Middlebrooks standing on second base with nobody out, Jackie Bradley Jr. hit a sharp grounder to Barton. The veteran didn't even so much as look at his bag, but instead fired the ball over to Donaldson at third to get a sliding Middlebrooks.
Jim Johnson proceeded to induce a double-play ground ball from Dustin Pedroia for the win.
"It's easy to say, 'I'll go over and tag first base and take the easy way out,'" said manager Bob Melvin. "What a terrific play. That's a gutsy play, because if he's wrong on that one, then they're in a position to move somebody over and win the game on a hit.
"Play of the game."
"That was, obviously, a play I thought about and have made before," said Barton, who hasn't made a start at first since April 28. "I anticipated a ground ball, knowing what [Bradley is] trying to do to get the guy over. I was still playing in -- just in case he bunted -- and it bounced right to me, just a little to my right. And [Donaldson] was around the bag, so as long as he was around the bag, I knew we had [Middlebrooks] in time."
Barton's instincts rewarded an extra-inning rally that began with a two-out double off the bat of Jed Lowrie, who ended up on third base following Chris Capuano's intentional walk to Donaldson and another walk to pinch-hitter Alberto Callaspo.
Red Sox manager John Farrell turned to ground-ball reliever Burke Badenhop to face Cespedes. The A's outfielder tapped a slow one to third baseman Middlebrooks, who made a nice barehanded grab but couldn't get it to first in time, allowing the go-ahead run to score.
"We've played a few of these games over the years with this group, but this is one where we get it handed to us a couple times and now we have to fight as hard as we can with basically no one on the bench," said Melvin. "Everyone contributed today. This team has shown to be very resilient, at times."
"You never want to get swept by a team," said Donaldson. "They've got a great ballclub over there -- and for us to continue to fight the way we did throughout the series, I think it shows the kind of guys we have here."
Having been held to just four runs over the first two games of this series, the A's got off to a quick start on Sunday. With two outs in the first, Donaldson drew a walk and proceeded to steal his first base of the year in advance of Moss' RBI single.
Donaldson reached base four times on the day, scoring twice, and has boarded at least once in each of his last 26 games.
In the third, Oakland's third baseman notched a two-out base hit and, in a familiar scene, headed home on another hit by Moss, this one a double. But Donaldson was called out on a close play at the plate, even after an umpire's review.
He would find his way home in the sixth, though, after getting hit by a pitch and scoring on Cespedes' fourth double in as many games.
Sonny Gray faced the minimum through four innings on 51 pitches, before giving up an RBI double to Grady Sizemore in the fifth. He ended the bases-loaded jam courtesy of a 1-2-3 double play on Bradley Jr.'s ground ball back to the mound.
"I faced Jackie Bradley in college with the bases loaded and one out, and he hit a ball right back to me and we turned a 1-2-3 double play," said Gray. "I was just picturing it in my head over and over and over -- and then I saw the ball coming to me, and the same thing happened. That was a huge turning point in the game."
Gray exited at 102 pitches after facing two batters in the seventh -- including A.J. Pierzynski, who led off the frame with a game-tying home run on a 3-2 fastball. He scattered six hits and two walks, while recording three strikeouts, over six-plus innings.
Oakland's bullpen carried things the rest of the way.
"We showed it was a complete team win today," said Gray. "It was a battle -- and you knew coming in, against this team at this park, it [was] going to be. It was really, really good to get this win going home."