SEATTLE -- With the Houston Astros in the midst of a tight playoff race and the season winding down, Lance McCullers might have been too wound up when he took the mound.

Houston's right-hander gave up one run early and another one late in the game, but three big Astros homers kept the team in playoff position.

"I was pretty amped for this game," McCullers said. "It's big. We're chasing a team for the division title, and we're being chased by guys for the wild card, so it was big to get this first win and hope we can build on this momentum."

George Springer, Evan Gattis and Chris Cater all homered for Houston, which is now just 1 1/2 back of the division lead thanks to the Rangers' loss to the Tigers.

In the clubhouse after the game, the Astros were gathered around the television watching the end of the Angels' game against Oakland. Disappointment rang out when Los Angeles came away with the win, keeping the Angels a half game back in the race for the second AL Wild Card spot.

Carter's home run in the seventh inning broke a 2-2 tie and gave the Astros the lead for good. He sent the first pitch he saw from Danny Farquhar (1-6) deep down the left field line for his 23rd homer of the year.

The offensive blasts were enough on offense, as McCullers' pitching -- and Houston's bullpen -- mostly kept the Mariners in check. Seattle has now lost seven games in a row, tying the Mariners' longest skid of the season.

"The fact is, we only scored two runs," Seattle manager Lloyd McClendon said. "We've got to get our offense going."

McCullers (6-7) gave up a run on a two-out single by Robinson Cano in the first inning and a solo home run to Ketel Marte in the sixth, but shut down the Mariners the rest of the way. McCullers allowed four hits and two walks while striking out seven -- the eighth time this season he's struck out at least seven.

"He was very, very amped early in the game," said Houston manager A.J. Hinch, echoing his pitcher. "He did a really good job of settling in."

McCullers came out in the seventh but gave way to reliever Tony Sipp after walking Mark Trumbo to lead off the inning. Sipp quickly picked off pinch runner James Jones and struck out the next two batters to end the inning.

Luke Gregerson came on to strike out the final two batters for his 30th save.

Seattle starter Roenis Elias settled down after giving up a pair of homers in the first inning. Elias only gave up one more hit in his six innings of work and kept the Astros scoreless after the first inning, striking out five and walking two. It was the first time in five starts Elias finished the sixth inning.

"The two home runs were not good," Elias said through a translator. "I thought they were good pitches. I was a little slow in the pace of the game, so they just kept telling me to pick it up, and once I picked it up I got better."

Marte led off the sixth with a towering home run to right field, his second of the season, to tie the game 2.

The Astros struck first to take a quick 2-0 lead with a pair of homers in the first inning.

Springer, the second batter of the game, got the Astros started with his 15th homer of the season to right field. Two batters later, Gattis hit his team-leading 27th homer off the out-of-town scoreboard.

The Mariners scored a run of their own in the bottom of the first. Kyle Seager drew a walk and advanced to third on Robinson Cano's two-out single. Trumbo followed with a single up the middle to score Seager and cut Houston's lead to 2-1.

The Astros know they likely need to keep coming out on top as the season moves to a close in order to assure themselves a spot in the playoffs.

"Everything matters," Carter said.

NOTES: The Mariners announced the hiring of Jerry Dipoto as the team's new general manager Monday. Dipoto resigned as the Angels' GM on July 1, a position he held since October 2011. Dipoto is the ninth general manager in Mariners history. ... Seattle manager Lloyd McClendon said he's not sure who will start Wednesday's game against Houston, but it's "highly unlikely" it will be LHP James Paxton. Paxton suffered a torn fingernail in his last start against Kansas City on Sept. 24, and McClendon said it's "50-50" whether he'll pitch again this season. ... The Astros entered Monday's game with a 17-11 all-time record at Safeco Field, the team's best mark at any active road stadium. ... This is the first contest of a six-game road trip for Houston to finish the regular season.