BALTIMORE (AP) For the first time in his major league career, Adley Rutschman was the focal point of a celebration at home plate that featured laughter, high-fives and the obligatory emptying of the dugout cooler on the head of the man who won the game.

“It felt awesome,” Rutschman said. “You've got so much adrenaline going at that point you don't really know what's going on. It's just cool to celebrate as a team.”

Rutschman led off the ninth inning with a tiebreaking homer off Trevor May, and the Baltimore Orioles also got a long ball from hot-hitting Ryan Mountcastle in an 8-7 victory over the struggling Oakland Athletics on Thursday.

Mountcastle's sixth home run, his fourth of the four-game series, sparked a four-run third inning that provided Baltimore with a 7-4 lead.

Oakland pulled even behind Brent Rooker, who homered twice and drove in five runs.

In the ninth, Rutschman drove the second pitch from May (2-1) into the center-field seats. Now in his second season after being selected No. 1 in the 2019 amateur draft, Rutschman finally got to experience the feeling of ending a game with a clutch home run.

“I was just trying to have a good AB there, do some damage,” said Rutschman, who recalled his only other walkoff homer being an inside-the-park sprint at Oregon State.

Félix Bautista (1-1) worked a perfect ninth to lay the groundwork for Rutschman's heroics.

After hitting a first-inning sacrifice fly, Rooker put the A's up 4-3 with a three-run homer in the third inning and tied the game at 7 with a solo shot in the fifth. It was his first career multi-homer game and first by an Oakland player this season.

“I'm feeling good and want to keep rolling, ” Rooker said. “I'm loving the chance to get to play and just hoping I can continue to help us win games.”

But the Athletics dropped three of four in Baltimore to conclude 1-6 trip that began in Tampa Bay.

The game featured a memorable Orioles debut by Ryan O'Hearn, who had two hits and three RBIs. Obtained for cash from Kansas City in January, O'Hearn opened the season in the minors despite batting .375 with three homers during spring training. Summoned from Triple-A Norfolk before the game, O'Hearn delivered a two-run single in the second inning and added a sacrifice fly in a four-run third that put Baltimore up 7-4.

“He shows up and right away impacts the game,” Baltimore manager Brandon Hyde said. “Great for him.”

It was O'Hearn's first three-RBI game since Aug. 4, 2021, against the Chicago White Sox.

Oakland starter Adam Oller yielded seven runs and eight hits over 2 1/3 innings before being replaced by Adrián Martínez, who struck out five in 3 2/3 hitless innings.

Facing the team he pitched for in 2021-22, Orioles starter Cole Irvin gave up six runs, five hits and a pair of walks in four innings. In the starts with Baltimore, Irvin is 0-2 with a 10.66 ERA.

“I'm not happy the way these first three have gone,” the left-hander said. “I'm not very happy about letting some teammates down. I just need to get better.”

TRAINER'S ROOM

Athletics: Reliever Domingo Acevedo received an MRI on his back that revealed a “minor strain,” according to manager Mark Kotsay, who called the result “good news.” Acevedo was placed on the 15-day injured list Tuesday.

Orioles: OF Anthony Santander (back) missed a second straight start but was available off the bench, Hyde said.

UP NEXT

Athletics: RHP James Kaprielian (0-1, 11.17 ERA) faces the visiting New York Mets on Friday night in the opener of a three-game set.

Orioles: RHP Tyler Wells (0-1, 3.27) helps Baltimore launch a three-game series in Chicago against the White Sox on Friday night.

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