Matt Chapman hit a go-ahead, two-run home run off Milwaukee Brewers All-Star Josh Hader in the eighth inning, delivering the host Oakland Athletics a 5-3 victory in the interleague game Thursday afternoon.
The homer was the A's second of the series off Hader (1-5), after Matt Olson had ended Tuesday's series opener with a walk-off shot in the 10th inning for a 3-2 win.
With the A's down 3-2, Robbie Grossman started off the eighth by drawing a full-count walk from Hader, who worked in all three games of the tightly contested series.
Chapman then drilled Hader's next pitch over the wall in center field for his team-leading 24th homer of the season.
The A's tacked on an insurance run later in the inning off Jay Jackson, with Jurickson Profar padding the lead with a sacrifice fly after singles by Khris Davis and Mark Canha.
Blake Treinen (6-3) got the win after working a scoreless top of the eighth. Closer Liam Hendriks recorded his 10th save with a 1-2-3 ninth that featured two strikeouts.
The Brewers never trailed until the eighth, scoring single runs in the first on a Ryan Braun single, in the fourth on a Trent Grisham sacrifice fly and in the seventh on a Jake Diekman wild pitch.
Grisham was making his major league debut after having been promoted from Triple-A earlier in the day. The outfielder, a 2015 first-round pick, was hitting .381 in 34 games at San Antonio.
He went 0-for-3 with an RBI.
The A's temporarily drew even in the third on Chad Pinder's ninth homer of the season, and got within 3-2 in the seventh on a Junior Guerra wild pitch.
Brewers right-hander Chase Anderson stood to get the win before Oakland rallied, having limited the A's to one run and two hits in six innings. He walked three and struck out five.
A's starter Homer Bailey, moved up a day when Oakland bumped Daniel Mengden from its starting rotation, also went six innings, charged with two runs on five hits. He likewise walked three and struck out five.
Canha went 3-for-3 for the A's, who now get a rare Friday off before a two-game home series against St. Louis this weekend.
The Brewers out-hit Oakland 7-6, with Mike Moustakas collecting two of their hits, including a two-out bunt single before Braun's RBI hit in the first inning.