PHOENIX -- Adam Eaton's blackout turned into a walk-off.
Despite being unsure of what pitch he hit or what to do as he rounded the bases, Eaton ended a wild game of momentum swings with the first walk-off homer hit into Chase Field's right field pool on Monday night, lifting the Arizona Diamondbacks to a 7-6 victory over the Baltimore Orioles.
"I'm not sure what happened -- I just blacked out," Eaton said. "I thought I hit a heater and found out later it was a slider."
Arizona has made an art of the comeback this season and pulled off a desert masterpiece to open the three-game interleague series against the Orioles.
Baltimore led 4-2 after roughing up Diamondbacks starter Wade Miley.
Arizona went up 5-4 in the seventh by stringing together three run-scoring singles, including one by Aaron Hill, who also homered for the third straight game.
Chris Davis tied the game in the eighth with a solo homer, not all that surprising since he leads the majors with 43.
The homer by Wil Nieves to lead off the eighth was a bit more unexpected. He hadn't hit one since last season and needed a friendly carom off the top of the wall in left to get it.
Arizona closer Brad Ziegler (6-1) had converted his first seven save chances this season, but was uncharacteristically off, giving up a tying sacrifice fly to Nick Markakis after the Orioles loaded the bases against him.
Eaton ended the night with its most surprising moment, putting an abrupt end to the momentum swings by sending the first pitch by Darren O'Day (5-2) into the pool in right-center to set off a wild celebration.
It was Arizona's second game-ending homer of the homestand -- Paul Goldschmidt did it to the Mets on Friday -- 23rd win in its last at-bat and 33rd comeback victory of the season.
"We could have got discouraged, we let some opportunities go, but battled back against a pretty good team," Diamondbacks manager Kirk Gibson said.
Baltimore got a solid start out of Scott Feldman, hit a pair of homers, twice battled back from late deficits and still wound up losing.
"Momentum is the next pitch you throw," Orioles manager Buck Showalter said.
Feldman put the Orioles in good position, only running into trouble in the second inning.
Parra was originally called out at home, but third base umpire Alfonso Marquez ruled Machado, who was standing on the bag, interfered with his progress toward the plate.
Feldman was good after that, allowing two runs -- one earned -- and four hits with eight strikeouts in 5 1/3 innings. He gave up nine earned runs in 9 2/3 innings his previous two starts.
"We had that one long inning, the second inning, that weird inning there," Feldman said. "Other than that, the offense picked us up."
Though Feldman left with the lead, the bullpen couldn't hold it.
Joe Thatcher, Arizona's left-handed specialist, couldn't hold the lead, either, giving up a no-doubt solo homer to left by Davis that tied the game at 5-all.
Nieves put the Diamondbacks back up quickly, hitting his first homer since Aug. 9, 2012, in his first game with the Diamondbacks.
Then it was Ziegler's turn to blow a lead.
Aided by first baseman Goldschmidt's inability to get the ball out of his glove on Nate McLouth's infield single, the Orioles loaded the bases with one out and Markakis followed with a sacrifice fly to tie the game.
The drama ended quickly in the bottom half, when Eaton hit his first homer of the season. He may not have known what happened, but his teammates sure did, mobbing him as he crossed the plate.
"He got something up, put a good swing on it and sent it to the pool," said Miley, who watched Eaton's homer from the clubhouse after allowing four runs and seven hits in seven innings. "It was a no-doubter."
Showalter received a nice ovation after being recognized in the first inning in his first game at Chase Field since 2000. He was the original manager of the Diamondbacks when they joined the league in 1998. ... The Diamondbacks have had an extra-base hit in 53 straight home games. ... Baltimore's Adam Jones went 0 for 4 to end a nine-game hitting streak. ... Orioles RHP Miguel Gonzalez will face the Diamondbacks for the first time in his career on Tuesday. He is 3-4 with a 3.68 ERA in 11 road starts this season. ... Arizona RHP Randall Delgado, who will start the series' second game against Baltimore, is 3-0 with a 2.81 ERA his past four starts.