BALTIMORE — There was little thought Ryan McKenna would come to bat Saturday when he trotted out to right field in the ninth inning as a defensive replacement to bring an end to Anthony Santander’s four-hit day just as Félix Bautista entered to close out a one-run lead.

Instead, McKenna produced Baltimore’s biggest swing of the day.

McKenna smashed his first career game-ending home run, a two-run shot to the opposite field off Seattle’s Justin Topa in the 10^th inning to seal the Orioles’ 6-4 victory over the Mariners before an announced crowd of 32,884 at Camden Yards on Saturday.

It was only McKenna’s second homer in 76 at-bats this season and the sixth of his career. And it gave the Orioles a lead they couldn’t give up after Seattle erased three deficits.

“He’s an animal off the bench,” Santander said. “That’s awesome, and I’m so happy for him. He’s been ready all game. He’s really paying attention to the game. When his opportunities come, he’s ready.”

Baltimore won in walk-off fashion for the fourth time this season and the second time with a home run. Adley Rutschman capped an 8-7 victory over Oakland on April 13th with a walk-off shot.

McKenna singled off Topa (1-3) a night earlier in the eighth inning of a 13-1 loss, and that appearance gave him a sense of the right-hander’s timing. Topa — the Mariners’ seventh pitcher of the day — got McKenna to foul off a first-pitch slider, then threw three consecutive 95 mph sinkers. The first two were balls. The third landed in the bleachers in right-center.

“It’s stuff you try to visualize, try to be prepared for that moment,” McKenna said. “Winning the game like that is always sweet.”

It was an unexpected conclusion to a game the Orioles seemed to have within reach a few times, most notably in the ninth inning when Bautista entered to try to convert his 10^th consecutive save. He quickly recorded two outs before Seattle designated hitter Mike Ford drilled a 100-mph fastball to right for his second homer of the day.

Bautista blew his first save since May 23rd, which was also the last time he had surrendered a home run.

The Orioles (46-29)  briefly threatened to win it in the ninth when Adam Frazier drew a one-out walk and Jorge Mateo entered to pinch-run. He was running when Cedric Mullins — activated earlier in the day from the injured list — skied a pop foul behind the plate, but Mateo forgot how many outs there were and was easily doubled up.

Mike Baumann (5-0) worked the 10^th for Baltimore, striking out two and stranding automatic runner Kolten Wong at second.

“Mike will flash you that kind of stuff, and he has that kind of ability,” manager Brandon Hyde said. “It’s an upper-90s fastball with a good curveball and a 93-mile-an-hour slider. He’s really just finding his way in the bullpen this year. Coming off a couple days rest, that was electric.”

Oriole starter Dean Kremer went a season-high seven innings, allowing solo homers to Ford and J.P. Crawford in the third inning and Julio Rodríguez in the sixth. He struck out five, yielded only two other hits and was in line to win his third consecutive start after Aaron Hicks’ solo homer in the sixth made it 4-3.

Baltimore almost added more in the seventh, only for Rodríguez to rob Ryan O’Hearn of a two-run homer by hauling in a shot near the bullpens in left-center.

Seattle nearly tied it in the eighth, getting consecutive singles off Yennier Cano before both men moved up on a soft grounder near the mound. With the infield in, shortstop Gunnar Henderson threw out Crawford at home, and reliever Danny Coulombe induced a grounder on his only pitch to escape the jam.

Earlier, Santander homered for the second consecutive day to tie it at 2 in the third, then poked a go-ahead single to right in the fifth. Santander enjoyed his first four-hit day since August 24th, 2021, and is hitting .409 (9 for 22) with four homers and seven RBIs over his last five games.

Meanwhile, his replacement in the No. 3 hole delivered arguably the most exciting moment of his major league career. McKenna entered the day with a .215 average in 251 games scattered over the last three seasons with Baltimore. He had only 12 plate appearances in June before becoming the first Oriole to hit a game-ending home run after coming off the bench since Rougned Odor did it May 20th, 2022, against Tampa Bay.

“When you’re with him every day, you really appreciate how much energy he brings to our team,” Hyde said. “Just the kind of person he is is phenomenal and he’s a great athlete that has helped us the last couple years in a lot of ways. So fun to watch him get this moment today. He’s earned it.”

Notes: Mullins went 0-for-4 with a walk in his first game since May 29th. He was also the automatic runner when McKenna homered in the 10^th. … Baltimore improved to 4-4 in extra innings this season and is 20-9 in games following a loss. … Reliever Mychal Givens is no longer scheduled to make his rehab appearance on Sunday for Triple-A Norfolk. Givens, who’s on the 15-day injured list with right shoulder inflammation, will be in Baltimore for a follow-up evaluation. … Outfielder Hudson Haskin was placed on Norfolk’s injured list with left hamstring tightness. … Norfolk second baseman Connor Norby was removed from the Tides’ game after fouling a ball off his left shin.