HOUSTON -- Everybody in the building knew the large shadow that was being cast from the on-deck circle in the ninth inning. For the Mariners, it was the last thing they wanted to see moving toward home plate. For the Astros, it meant they still had a glimmer of hope in Game 1 of the American League Division Series at Minute Maid Park.

So when rookie shortstop Jeremy Peña slapped a two-strike, two-out single to center field to keep the Astros’ hopes alive, the stage was set for Yordan Alvarez. The slugger crushed the second pitch he saw from left-hander Robbie Ray and sent it sailing into the upper deck in right field for a dramatic walk-off three-run homer that sent the Astros to a stunning 8-7 come-from-behind win over the Mariners on Tuesday.

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“I think it's one of the most special moments that I've had in my career, having [my parents] there, and even for just the city of Houston,” Alvarez said. “They know that we're a team that never gives up. So just being able to get that hit right there was one of the most special moments of my career.”

The ballpark erupted with enough noise to be heard in Seattle, with Alvarez getting mobbed by his teammates in a mad celebration at home plate. Orange-clad Astros fans stood at their seats in disbelief for several minutes after the game, trying to digest what had just happened.

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“The place was on fire tonight,” Astros third baseman Alex Bregman said. “The fans were unbelievable. It was so awesome to have a packed house here. The energy was flowing. We felt it. We felt them. We love when they're loud. Just that environment was awesome. Yordan hitting a homer was crazy.”

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The Astros, who trailed, 7-3, through seven innings, got a two-run homer from Bregman in the eighth and Alvarez’s no-doubt blast to right to win it in the ninth. The stunned Mariners -- who rallied from seven down to beat the Blue Jays and advance Saturday -- had the tables turned on them by their AL West nemesis, the Astros.

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Instead of getting a rare win at Minute Maid Park, the Mariners fell to 7-31 in Houston since 2019.

“It's a tough one, there's no question about it,” Mariners manager Scott Servais said. “I thought we played a very good ballgame today. We did a lot of great things offensively. Certainly we got on [Justin] Verlander early in the game and did exactly what we needed to do there.”

Alvarez’s Statcast-projected 438-foot blast was the first walk-off home run in postseason history by a team trailing by multiple runs. It was the second walk-off homer in postseason history by a team down to its final out. The other was Kirk Gibson's game-ending homer off Dennis Eckersley in Game 1 of the 1988 World Series.

“Boy, that was probably one of the most exciting games that I've been a part of,” Astros manager Dusty Baker said.

In the history of best-of-five postseason series, Game 1 winners have gone on to win the series 102 of 144 times (71%). In Division Series with the current 2-2-1 format, teams winning Game 1 at their home ballparks have advanced 34 of 47 times (72%).

“I think we enjoy these kinds of games,” second baseman Jose Altuve said. “Like I said yesterday, we're not trying to be heroes, but Yordan was a hero tonight because the moment was perfect for him and he executed.”

The Mariners jumped on Verlander for six runs and 10 hits in four innings, taking a 7-3 lead on Eugenio Suárez’s homer in the seventh. The Mariners had a 98% win probability when Peña lined out to start the eighth, but Houston chipped away against one of the best bullpens in baseball.

“We know how important 27 outs are, especially in the postseason,” Bregman said. “I thought Dusty did a great job. He managed this game like we were going to win it from the first pitch. He has the ultimate confidence in every single person on this roster. You saw that today with how many guys were used.”

Now the Astros will turn to left-hander Framber Valdez in Thursday’s Game 2 to try to send the Mariners to the brink of elimination ahead of the first playoff game in Seattle in 21 years in Saturday’s Game 3 at T-Mobile Park.

“You can’t count us out,” Peña said. “Our pitching staff has been dominant all year, so great teams do that. We pick each other up, and that’s what we did tonight.”