Adam Eaton deposited the first pitch he saw in the ninth inning into the pool beyond the wall in right-center, and the leadoff home run sent the Arizona Diamondbacks past the Baltimore Orioles, 7-6, in the first of three interleague games at Chase Field.
Chris Davis tied things in the away eighth with a solo home run -- his league- leading 43rd of the season -- and Wil Nieves answered in the bottom half with his first of the year to nearly the same spot, though his hit the top of the wall and bounced halfway up the left-field bleachers where Davis' landed.
Brad Ziegler was unable to close out the victory in the ninth, as he loaded the bases with one out and gave up a sacrifice fly to Nick Markakis.
Ziegler (6-1) retired Manny Machado to get out of the inning, and Eaton connected on his first home run of the season on Darren O'Day's (5-2) first pitch to give the D'backs their eighth walk-off win and the 24th victory in their last-at-bat.
"I thought I hit a heater, but apparently I hit a slider. I caught it out front and was happy with the result," Eaton said.
Like Eaton, Aaron Hill had two hits, a home run and two RBI in the win, Arizona's fourth in six games.
Brian Roberts went 2-for-3 and knocked in a pair of runs, while Matt Wieters added a solo homer for Baltimore, which fell to 4-2 in its eight-game road trip against NL West opponents.
Neither starter factored in the decision. Arizona's Wade Miley gave up four runs on seven hits over seven innings, and his counterpart, Scott Feldman, last just 5 1/3 innings and was charged with two runs -- one earned -- on four hits and a pair of walk.
Miley's 10th wild pitch of the season allowed Markakis to score in the first inning, and Roberts singled in J.J. Hardy in the second for a 2-0 lead.
Arizona got the runs back in its half of the second, which started with Hill launching his third home run in as many games and saw Gerardo Parra score on a questionable defensive interference call on Machado.
"It's the wrong call, a lapse in judgement," said Orioles manager Buck Showalter said, referencing Parra barely bumping into Machado as he was rounding third base. "(Parra) was out by three steps. It's unfortunate in a one-run game."
Parra wasn't playing no-doubles defense when Roberts doubled over his head with two outs in the fourth inning, allowing Steve Pearce to score the go- ahead run from first for a 3-2 Baltimore lead.
Wieters took Miley deep over the center-field wall in the sixth for his 16th home run of the year, but the Diamondbacks took the lead, 6-5, in the seventh on RBI singles from Eaton, Hill and Martin Prado.
The D'backs lead the majors with 25 one-run wins and are 10-1 in their last 11 interleague game at Chase Field ... Feldman recorded eight strikeouts ... The D'backs placed outfielder Cody Ross on the 15-day disabled list Monday due to a disclosed hip, optioned pitcher Zeke Spruill to Triple-A Reno and recalled pitchers Chaz Roe and Tyler Skaggs from Reno ... The Orioles have never won a series against Arizona in four tries.