SEATTLE -- Astros starter Hunter Brown struck out nine batters in six strong innings and third baseman Alex Bregman clubbed a homer that put his team in position to get a win.

But the overriding topic of conversation in the Astros clubhouse Tuesday night was how it all unraveled in the eighth inning.

The Mariners rallied for three runs off setup man Ryan Pressly in eighth, with a throwing error by Bregman helping Seattle along the way, to beat the Astros for the second night in a row, 4-2, at T-Mobile Park. The loss dropped the Astros 5 1/2 games behind Seattle in the American League West race.

“It’s never fun losing to anybody,” Pressly said. “We just got to figure it out.”

Brown held the Mariners to one run in six innings while striking out a season-high nine batters, giving him back-to-back quality starts. Bregman’s fourth-inning, two-run homer off Luis Castillo put the Astros ahead, 2-1, and Houston was six outs away from a win after Bryan Abreu pitched a 1-2-3 seventh inning.

So how did it go awry in the eighth?

Pressly pointed to the leadoff double, a shot off the bat of Mitch Haniger that went into the left-field corner. He then walked nine-hole hitter Ryan Bliss before striking out J.P. Crawford.

“Just couldn't finish some hitters,” Astros manager Joe Espada said. “That’s where everything kind of unraveled.”

Against Josh Rojas, Pressly executed the pitch he wanted -- a slider down and in -- but Rojas turned on it and hit it off the glove of a diving José Abreu at first base to score pinch-runner Jonatan Clase.

The blown save was the 10th of the season for Houston.

“Other than [the Haniger double], I feel like I made my pitches,” Pressly said. “The one to Rojas was down and in where I wanted. It was perfectly executed, and he just turned on it and hit it down the line. Mix in some bad luck with it.”

Julio Rodríguez followed with a dribbler to Bregman, who didn’t have time to get Bliss at the plate with the go-ahead run. His throw to first base to try to get Rodríguez sailed wide of Abreu and into foul territory, and Rojas scored from second base to give the Mariners a 4-2 lead.

“I definitely should have just ate it and not thrown the ball,” Bregman said. “Obviously, a good runner at third base and Julio is an incredible runner as well. As soon as I looked home trying to get that guy, I probably should have just ate it and not thrown it. It was kind of perfectly placed there for him to go on contact.”

Rojas said the plan of attack against Pressly was to “beat the spin to the spot.”

“He's got a really good fastball that you have to be aware of as well,” he said. “So you can't really sit on spin, but you're just really trying to beat all his pitches to the spot. And yeah, I mean he threw a well-located [slider] there and not exactly where I wanted to hit it. I was trying to get it to stay in the air to right-center on the spin coming towards me. He located well, down-and-in, and luckily I got it by Abreu."

Brown retired 15 of the final 16 batters he faced, including seven by strikeout, and threw 87 pitches before turning the game over to the bullpen. He gave up three consecutive singles in the first inning, including an RBI single by Rodríguez, who was later thrown out at third base by left fielder Yordan Alvarez while trying to advance on a Cal Raleigh knock.

“Limiting free passes, that is something for any pitcher, is a focus,” Brown said. “Any day that you can not walk somebody -- I did end up putting a guy on a hit by pitch -- is a good day.”

Bregman, bumped down a spot in the batting order to fifth Tuesday, responded by putting the Astros ahead with his fifth homer of the season and went 2-for-4 for his second multihit game in his past three. But the Astros were held to five hits and have only 11 in two games against Seattle.

“We just didn’t get the job done tonight,” Bregman said. “Obviously, we want to get all these games, especially against our division opponents. You learn from it and come back tomorrow and get after it.”