SEATTLE -- Though the Mariners are the team in a tight playoff race, it was the Houston Astros who played like contenders Tuesday night.
Logan Morrison homered off McHugh in the eighth to tie it, but Houston countered and dropped the Mariners a half-game out in the race for the second AL wild card.
"This type of win builds character," said interim Astros manager Tom Lawless, who is 5-2 since taking over when Bo Porter was fired last week. "They have the confidence and they know they can win. When you have that, you come out ahead a lot of times. And it's someone different every night."
"We had the matchup we wanted," Mariners manager Lloyd McClendon said. "We had the groundball we wanted. It just took a bad hop. Tough break."
Houston (64-81) has won 13 of 21, and the Astros are nearly halfway through a stretch that has them facing playoff contenders in 18 straight games.
"It's a good sign of things to come for this organization," McHugh said.
McHugh (9-9) permitted only two hits in eight innings -- an infield single in the fourth and Morrison's long homer off the facade of the second deck in right field. The right-hander struck out four and walked none.
Josh Fields worked the ninth for his fourth save.
"The way we lost tonight is not ideal. We take it a little harder. But it is what it is: one game," Morrison said. "We still control our own destiny so if we continue to take care of business, we'll be fine."
Roenis Elias pitched six innings for the Mariners, allowing one run and six hits. He walked two and struck out four.
The Astros scored with two outs in the fourth. With Jake Marisnick on first, Singleton sent a line shot to right that hit the yellow line at the top of the 8-foot wall.
In his attempt to gather it in, right fielder Michael Saunders bobbled the ball twice. That allowed Marisnick to beat the relay home on the double.
A replay review kept the Astros off the board in the sixth.
With two outs and runners on first and second, Singleton bounced a grounder to the right of Morrison at first base. He made a high toss to Elias covering. Elias leaped for the ball and came down on the bag at the same time as Singleton.
Singleton was ruled safe, and Chris Carter raced across the plate. McClendon challenged the call at first, which was reversed.
Joe Beimel pitched to one batter in the ninth for his 50th appearance. That gave the Mariners seven relievers with at least 50 appearances, matching the major league record set by the 2002 Atlanta Braves.
Lawless, who took over the team last Tuesday, said he hasn't talked to anyone in the front office but certainly would like to stick around after this season.
"I've been in baseball forever. We'll see what happens," he said. "Hopefully, I'll be included in the mix and we can just take it from there. Maybe this is a nice tryout for me, to see what I can do and see how everybody responds and how we're going about our business."
SUCCESSFUL IN SEATTLE
In two starts at Safeco Field, McHugh has given up just one run and allowed five hits while striking out 16. Over his last eight starts, he is 5-0 with a 1.69 ERA.
"I had better fastball command than I've had in a while. It felt good coming out of my hand," McHugh said. "It's nice to be able to put the ball where you want. It was pretty frustrating to battle almost eight innings and (Morrison) puts a swing like that on it. You tip your hat, but it was still a tie game and we had a job to do."
Mariners: An MRI revealed bone spurs in OF Dustin Ackley's painful left ankle. He missed his third straight game. The club hopes he can return for the weekend series against Oakland.
Mariners RHP Hisashi Iwakuma (14-6, 2.97 ERA), who starts the series finale Wednesday, is 6-1 with a 2.70 ERA in his last eight starts. He has as many wins as walks this season.
Iwakuma will be opposed by RHP Nick Tropeano, making his major league debut. The September call-up was a fifth-round selection in the 2011 draft.