SEATTLE — The Houston Astros’ playoff momentum was halted Sunday by a pitcher they had never faced – and likely will have to face again.

Ariel Miranda (5-1), a Cuban defector acquired by the Seattle Mariners in a July 31 trade with Baltimore, held the Astros to just three hits and two runs over his seven innings in Seattle’s 7-3 victory.

Seth Smith powered up a pair of home runs and had four RBI in support as the Mariners moved ahead of the Astros in the congested wild-card race.

Houston (78-71) is a half game behind both the Mariners (79-70) and Detroit in the race for the wild card spots.

“He (Miranda) has a good fastball and a good split finger-change thing that he throws,” Astros manager A. J. Hinch said. “Our guys hadn’t seen a ton of him…he did a good job challenging us, just above the zone and we swung under today and hit a lot of pop-ups in the infield, a few balls to the outfield. A couple balls to the track that could have changed the game a little bit. He kept enticing us with fastballs.”

That enticement will continue in the final week of the season. The Mariners play another three-game set with he Astros in Houston, Sept. 26-28, and Miranda likely is on schedule to start that series’ final game.

Miranda’s seven innings was his longest outing in 10 starts with Seattle. He walked one and struck out eight.

“Heck of an outing,” Mariners manager Scott Servais said. “He’s on a heck of a roll. We certainly needed it. He’s gained so much confidence. You can certainly can see it.”

Miranda has won all four of his starts in September. He said, through an interpreter, “it’s been a dream of mine (to be in a playoff chase) but never been there. It’s really great to get there. I’m happy with the work I’ve been doing and happy to help the team.”

Smith had a solo shot in the third and a three-run blast in the fourth, both on 3-1 pitches from Doug Fister (12-12), who went just 3 2-3 innings.

“I was just trying to attack with my sinker; he put a couple good swings on balls – clearly,” Fister said. “I just didn’t execute today, that’s what it comes down to. Balls down, balls up, all over the place. I let my team down.”

Smith had been 0-for-10 in his career against Fister but the eight-year veteran had a plan.

“Guys know what they’re doing when they are pitching and able to pitch to the corners,” Smith said. “You try to take the close ones, try to get into a good hitter’s count when they come after you.

“You’re constantly learning, how to approach at-bats, knowing what kind of swing you have going into a game, knowing what the pitcher is trying to do to you,” Smith said. “Over the course of a career you kind of fit the pieces a little better together.”

RECORD WHIFFS

With Jandel Gustave’s strikeout of Shawn O’Malley in the sixth, the Astros staff established a club record for strikeouts with 1,283. They’ve done it without even a 200-strikeout pitcher. “For the most part we have a few guys who can spin their breaking balls when they need to,” manager A.J. Hinch said. “and the changeup is a big component of our pitching staff.”

SLOW START; FAST FINISH

Nori Aoki, who was sent to the minors twice this season to work on his offense, has found his batting eye this month. Entering the game, he was hitting .387 in September, fifth best in the American League. He had been hitting .255 overall to start the month. For his career, he is a .324 hitting in September, fourth best among active players. He had two hits Sunday.

TRAINER’S ROOM

Mariners: 1B Adam Lind had not played since Sept. 12 with a sprained finger in his right hand but was back in the lineup Sunday, missing five games.

UP NEXT

Astros: RHP Brad Peacock (0-0, 2.70) will make his third start, seventh appearance, in his effort to win his first game since 2014. Last time ou, Sept. 13, he was solid, going six innings and allowing just three hits and one run in a 3-2 loss to Texas. Now the Astros are counting on him to step up at the most critical stage of the season. He is 1-4 with a 4.97 ERA in nine career appearances against Oakland.

Mariners: RHP Taijuan Walker (6-10, 4.28) is coming off his best starting effort of his career (59 starts). He allowed just three hits and no runs – first career shutout – in an 8-0 win over the L.A. Angels. He had a no-hitter through 5 2-3 innings. He is 0-2 with a 3.66 ERA in three career starts against the Blue Jays but has not faced them this season.