SEATTLE -- The struggling Seattle Mariners traded for rookie left-hander Ariel Miranda at the deadline, not expecting the 27-year-old Cuban product to be a factor in their run toward postseason possibility.

And yet Miranda, who was acquired for veteran starter Wade Miley, has been a huge part of the Mariners getting back into wild-card contention. He turned in his finest start yet, allowing just two runs and three hits in seven innings to lead Seattle to a 7-3 win over the Houston Astros on Sunday.

"(Getting to the postseason has) been a dream of mine, something I've never had the opportunity to do," Miranda said through an interpreter after Seattle (79-70) moved within two games of Toronto in the American League wild-card race. "It's something where it would be really great to get there."

The Mariners still have work to do, beginning with a three-game series against the Blue Jays that opens Monday at Safeco Field.

"We just have to keep doing what we're doing," Seattle center fielder Leonys Martin said. "We just never give up and fight every game."

Seth Smith hit two homers as the Mariners salvaged the final game of the series. Smith's 15th and 16th home runs, both of which came off Astros starter Doug Fister, helped the Mariners jump out to a 7-1 lead in the first four innings.

Houston (78-71) fell four games behind Baltimore three behind the Blue Jays.

Miranda (5-1) allowed two runs -- on two solo homers -- and three hits in seven innings. He struck out eight during the best start of the 27-year-old rookie's young career.

"Our guys hadn't seen a ton of him," Astros manager A.J. Hinch said. " ... He kept enticing us with fastballs."

Smith led off the third inning with a solo homer, then added a three-run shot in the fourth. He went 2-for-2 while scoring three times and driving in four runs.

Leadoff hitter George Springer and shortstop Carlos Correa each had a solo homer for the Astros. It was Correa's 20th home run of the year, giving the 21-year-old -- he turns 22 on Thursday -- back-to-back 20-homer seasons to open his career.

Fister (12-12) allowed seven runs and eight hits in 3 2/3 innings.

"He'll keep grinding and trying to find a solution," Hinch said of Fister, who has allowed six or more runs in three of his past four starts. "He's the consummate pro, so we'll expect him to be better next time."

Houston third baseman Yuli Gurriel drove in his third run in two days with a two-out RBI double in the eighth that cut the Astros' deficit to 7-3.

Seattle third baseman Kyle Seager gave the Mariners a 2-0 lead with a two-out, two-run double in the first inning.

Springer hit his 28th home run of the season to cut the lead to 2-1 in the top of the third. Smith led off the bottom of the third with a solo shot, his 15th home run of the season, to open a 3-1 Seattle lead.

After Seattle's Norichika Aoki doubled in a run in the bottom of the fourth, Smith added a three-run shot for a 7-1 advantage.

Correa's seventh-inning home run pulled Houston within 7-2. Correa had two of the Astros' five hits in the loss.

Seattle, which had just one run and 10 hits in the first two games of the series, broke out for 11 hits and seven runs on Sunday.

"It's big to win the game," Smith said.

NOTES: Mariners 1B Adam Lind, who had missed five games with a sprained finger, was back in the lineup Sunday. He went 1-for-4 in the win. ... Houston had 3B Yuli Gurriel back in the No. 2 spot in the order Sunday, one day after he delivered the game-winning runs out of that spot. ... Seattle opens a three-game homestand with the Blue Jays on Monday. ... Houston opens a three-game series at Oakland on Monday.