SEATTLE -- After losing their spot atop the American League West two weeks ago, the Houston Astros are now beginning to lose their grip on the AL wild-card race.

Seattle rookie Shawn O'Malley delivered a two-run, two-out, tiebreaking single in the eighth inning as the Mariners beat Houston 6-4 to knock the Astros out of a playoff position for the first time this season.

"We've had some bad luck the last few weeks," Astros right fielder George Springer said, "but at some point you've got to stop making excuses and just go out and play."

Houston (83-75) fell a half-game behind the Los Angeles Angels in the race for the final American League wild-card spot. The Astros also dropped to 2 1/2 games behind Texas in AL West standings with just four games left on Houston's schedule.

"It's a very frustrating game," manager A.J. Hinch said after the loss. "And it's obviously magnified given the time of year."

O'Malley's single to left-center broke a 4-4 tie and helped Seattle (75-83) snap a six-game losing streak. The rookie center fielder came off the bench and finished 1-for-2.

Mariners closer Tom Wilhelmsen, who came on with one out in the eighth inning of a tie game, earned the win after pitching 1 2/3 scoreless innings. Wilhelmsen (2-2) got his first victory since May 15.

Houston's Oliver Perez (0-3) took the loss after one of the two batters he faced, outfielder Seth Smith, singled and eventually came around to score the game-winning run on O'Malley's hit.

"This is what we play for, and we have to be prepared for these kind of games," Perez said.

The Mariners had four consecutive players reach base with two outs in the eighth, with reliever Pat Neshek giving up two singles and a walk after coming on for Perez with a runner on first. Neshek allowed a single to first baseman Mark Trumbo and walked pinch hitter Franklin Gutierrez before O'Malley delivered the big hit.

"I feel like everything I'm doing right now isn't working out," said Neshek, who is 0-3 with two blown saves in September.

Houston got a baserunner in the top of the ninth, but Springer, who had three hits and an RBI, flied out to right to end the game.

"The fortunes were with us tonight," Seattle manager Lloyd McClendon said.

Mariners second baseman Robinson Cano hit a two-run homer in the sixth, tying the score 4-4, and he finished with three RBIs. Houston left fielder Marwin Gonzalez hit a tying home run in the fifth, with his solo shot pulling the Astros even at 2-2.

Houston starter Mike Fiers allowed five hits and four runs (three earned) over 5 2/3 innings. It marked the fourth start in a row that Fiers was not involved in the decision.

"Just not getting it done," Fiers said when describing an outing that saw him serve up the homer to Cano. "We had the game right there with the lead, and I had to get one more out (in the sixth) to keep the momentum going. ... You don't want to throw a fastball down to Robinson Cano. I did, and he took advantage of it."

Springer's two-out RBI double, his third hit of the night, gave the Astros a 3-2 lead in the fifth inning. Springer drove in catcher Hank Conger, who doubled after Gonzalez tied the score with his 12th home run of the season.

The Mariners took a 2-1 lead in the bottom of the first inning on a pair of sacrifice flies. Shortstop Ketel Marte led off the frame with a single and moved to third on a double by third baseman Kyle Seager. Designated hitter Nelson Cruz then drove in his 91st run of the season with a flyout to left, and an error on the throw home allowed Seager to move to third. One batter later, Cano flied out to left to score Seager.

Houston's initial run came on an RBI by shortstop Carlos Correa after the first two Astros hitters reached on singles. Correa's groundout to second base scored leadoff hitter Jose Altuve from third for a 1-0 lead.

Seattle starter Vidal Nuno allowed three runs on six hits over five innings. He struck out five without issuing a walk.

Houston led the AL West for the first five months before finally getting passed by Texas earlier this month. The Astros are still hoping to catch the Rangers, but the bigger race could be the battle with Los Angeles for the second wild-card spot. Houston had a hold on that until Tuesday night, when both the Angels and Rangers won.

"We just have to go out and play," Springer said. "Four more to go; anything can happen."

Fiers added, "Everyone's got to put this one behind them. We've got another game tomorrow. We'll turn the page, and tomorrow will come."

NOTES: Astros SS Jed Lowrie strained his left quad in the fifth inning and had to come out of the game. He said afterward that the injury will be re-evaluated Wednesday. ... The Mariners introduced new executive vice president and general manager of baseball operations Jerry DiPoto. DiPoto spent five years as the Los Angeles Angels' GM but was fired in July, reportedly because of a rift with Los Angeles manager Mike Scioscia. DiPoto denied any kind of personality conflict with Scioscia and said that he was impressed with Mariners manager Lloyd McClendon during a Monday meeting. ... Mariners LHP James Paxton (torn fingernail) was shut down for the remainder of the season, McClendon announced. Seattle plans to use a pitch-by-committee approach for Wednesday's game, with a to-be-named reliever making a spot start. ... With his home run Tuesday night, Mariners 2B Robinson Cano reached the 20-homer mark for the sixth time in the past seven seasons.