One strike away from completing what would have been his second consecutive terrific outing, Astros starter Lance McCullers Jr. was left to digest disappointment.

Mariners first baseman Evan White, who had struck out in his first two at-bats, slugged a two-out, three-run homer in the seventh inning to break the game open and beat the Astros, 6-1, in the series opener Monday night at T-Mobile Park.

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With that, the Astros’ magic number to clinch the second playoff spot in the American League West remained at three, with the Mariners now three games behind them with six games remaining in the season, including two more in the series in Seattle. The Angels are only one-half game behind the M’s.

“What are you going to do, just going to give them the next two days?” Astros manager Dusty Baker said. “They have to earn the next game first. The Angels are knocking at the door behind them. We’ve just got to take care of our own business.”

With the Astros’ loss, the A’s clinched the AL West title, ending the Astros’ run of three consecutive division crowns.

In two starts since coming off the injured list, McCullers hasn’t allowed an earned run in 13 2/3 innings -- all four runs he allowed Monday were unearned -- but the offense hasn’t scored a run while he’s been on the mound. Mariners lefty Marco Gonzales threw eight scoreless innings as Houston’s offensive woes continued.

“It’s just a tough patch,” McCullers said about the Houston bats. “These guys have been here for me many times when I haven’t been throwing the ball or whatever the case. I wouldn’t pick anybody else over the guys we’ve got. We did get quite a few hits today, damn near seven, eight, nine, whatever it was. We just have to start stringing them together, that’s all.”

McCullers threw a season-high 102 pitches and carried a no-hitter into the sixth inning. In the seventh, a four-pitch walk to Kyle Lewis got the Mariners started. Kyle Seager reached on an error by second baseman Jose Altuve, and Ty France broke the scoreless tie with a double down the left-field line. McCullers came back to record a pair of strikeouts but couldn’t put away White, who swatted a 2-2 hanging curve over the left-field wall.

“Don’t mind the pitch,” McCullers said. “Just needed to be a little bit down or a little bit further out, and we roll and we have a really good chance to win that game.”

Still, McCullers’ performance in his past two starts bodes well for the Astros going forward. With Justin Verlander set to undergo Tommy John surgery and unavailable for the playoffs, an effective McCullers could loom large in the playoffs.

“I was on the IL because I had an irritated nerve from a flight,” said McCullers, who didn’t record an out Sept. 4 in Los Angeles and was put on the IL. “If I would have been smarter and not even pitched that game in L.A., I probably would have been [out] a day or two. I feel like I’m throwing the ball really well, and tonight was no exception. I thought I threw the ball excellent. I just didn’t make a pitch.”