The biggest swing of the season for the Astros belonged to Martín Maldonado, and it put his team on the verge of clinching its fifth playoff berth in the last five seasons.

With the offense in a month-long malaise and the rebuilding Mariners clipping at their heels for the second playoff spot in the American League West, the Astros got a huge lift from Maldonado that allowed the visiting dugout at T-Mobile Park to exhale.

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Maldonado’s three-run homer in the sixth inning Tuesday night capped a five-run outburst -- Houston’s biggest inning since scoring five in the ninth to win at Dodger Stadium on Sept. 12 -- to send the Astros to a 6-1 win over the Mariners that reduced Houston’s magic number to two.

“I would say probably the best [swing] I took all year, especially in the situation and the way I have been lately,” said Maldonado, who has 12 of his 24 RBIs this year against Seattle.

The Astros, who got four hits from Kyle Tucker and a sixth-inning homer from Michael Brantley, are 8-0 when they have an inning with five runs or more.

“It’s fun when you get some hits,” manager Dusty Baker said.

If the Astros beat the Mariners and the Angels lose to the Padres on Wednesday, Houston would clinch a playoff spot. The current postseason projections have the Astros as the sixth seed, set to visit the division-champion Oakland A’s in the best-of-three Wild Card Series.

Houston’s playoffs hopes should rise if the offense can build on Tuesday’s game and keep scoring runs and the starting pitching stays on course. Astros starters, led by Framber Valdez and Lance McCullers Jr., have posted a 1.84 ERA in the team’s last eight games, six of which have been quality starts. The Astros could be a difficult matchup in the playoffs.

“After we get there, we know what we have to do to win games,” said Maldonado, who caught Valdez on Tuesday. “This team has done it for the past three years. It’s a matter of getting the at-bats together and the pitches together. We know how to win games, especially when the playoffs start.”

Valdez (5-3) completed seven innings for the sixth time and topped 100 pitches (108), also for the sixth time. The workhorse lefty finished his outing by striking out the side in the seventh, giving him eight strikeouts. He allowed one run and five hits and had no walks.

“I felt strong at the end, like always,” Valdez said. “What happens is the game gets tight and gets deeper, I turned it up as well. I have to attack the game and win the game and not let the game win me.”

The emergence of Valdez as one of the better lefties in the AL this season is surprising. He struggled to throw strikes in his first two years in the big leagues, averaging 5.7 walks per nine innings with a 4.60 ERA and 1.52 WHIP. Valdez, who’s always had a plus curveball, worked with a psychologist in the offseason to improve his demeanor on the mound and body language. He’s become a different pitcher.

“I would say that he really controls his emotions,” Maldonado said. “He always had the good stuff. Last year, even the year before when I caught him, he’s still the same guy. It seems like he cares more now, seems like he’s developed better. That not much stuff gets into his head, I would say.”

Valdez didn’t walk a batter for the first time this season Tuesday and is issuing just 2.04 walks per nine innings. Now the Astros must decide whether he’ll be a better weapon in the bullpen or the rotation, but it’s clear he’ll be a big part of Houston’s plans in October.

“I’m laughing and staying loose, and that's the only way I can execute a pitch ... is to have a good attitude above everything else,” he said.