It was the third hit of the night for Donaldson, who fell a triple short of hitting for the cycle, and it came just an inning after he made a bold move by stealing third base with reliever Philip Humber on the mound, allowing him to score on a Yoenis Cespedes groundout for the go-ahead run.
How rare was it? Donaldson has just four stolen bases this year.
How big was it?
"At the time," said manager Bob Melvin, "that was just as big as the homer, if not bigger."
"After they made a pitching change, I knew he wasn't necessarily fast," Donaldson said. "I wanted to do it the first pitch, but he kind of looked at me a little longer than I wanted. I saw he still went really high. Obviously, I'm not a burner. When he went high like that, it gave me the opportunity to try to take off right there. I did it the second pitch."
Donaldson did it all, also contributing to a two-run third with a leadoff double. Jed Lowrie followed with his own two-bagger to bring in a run, and Nate Freiman's infield single one out later knotted the game at 3, after the Astros had scored just as many in the top half of the frame off A.J. Griffin.
Houston came back to regain the lead in the fourth on Jonathan Villar's bunt single, before the A's answered with two more runs.
Griffin, finally, found his groove in his final two innings, after finishing the first three at 72 pitches. Oakland's righty struck out five of his final six batters to finish with a career-high-tying nine strikeouts.
That gave the A's time to put the game away for good.
"Early on it was a little spotty, fastballs at times were up," Melvin said. "But then really, last couple innings he did his best work, no question. In a game that you'd like him to get through the sixth inning."
"That was huge," Griffin said. "Going out there in the fourth inning, kind of struggling a little bit, Bob stuck with me, and that helped my confidence a little bit. I wanted him to be happy with his decision. I just tried to go out there and execute my game plan, keep them off-balance, and the results were there. It worked out."
Donaldson's 21st homer of the season, this one off Humber, improved the A's to 52-6 when they hit more home runs than their opponent.
Lefty Sean Doolittle, pitching for the first time since Sunday, tossed 1 1/3 scoreless frames. Ryan Cook came in to get the final two outs of the eighth, and Grant Balfour pitched a one-run ninth for his 37th save of the season.
But it didn't come easily. And that's becoming a familiar tune when the closer is the mound, as he's allowed runners in each of his past six appearances. Balfour needed 35 pitches to get through this one, in part because of Eric Sogard's botched attempt at a game-ending double play that extended the ninth.
By that point, Melvin already had the bullpen in action.
"I'm not going to tell you how far I was going to take him," he said, "but it was a little shaky again. He's not happy about it. Certainly if we don't make an error there, it's probably a little different. You know, you got to look at body of work, too. We'll continue to go accordingly, this isn't the best stretch right now, and we'll monitor that."
At the very least, Melvin can sleep well knowing his club's in first place, right?
"You know what? I hadn't really thought about that," he said, smiling. "I'll tell you tomorrow."