(Photo credit: Troy Taormina-USA TODAY Sports)

This past weekend might have determined how the American League West was won.

Houston, Texas and Seattle entered play Friday all within a half-game of each other. The Rangers, after leading the division for most of the season, regained control with a three-game sweep of the visiting Mariners, while the Astros inexplicably lost three straight at home to lowly Kansas City.

The Astros and Mariners, who open a three-game series Monday night in Seattle, might have let their chances at a division title slip away, but they're still battling for a wild-card berth.

The Astros (85-71) have a half-game lead on the Mariners (84-71) for the final playoff spot in the American League.

"It sucks not being able to win right now and getting swept, but we've just got to forget and go to Seattle and play," Astros outfielder Mauricio Dubon said after Sunday's 6-5 defeat. "Everybody knows what's going on. So we've just got to go there and be focused and try to win baseball games."

First baseman Jose Abreu said he's confident the Astros can turn it around.

"The champions always have pressure and I think the guys know what they need to do to be able to get out of this," Abreu said through a translator. "We haven't got the results (we wanted) but we know what we need to do and it starts (Monday)."

The Mariners seemed slightly more optimistic after nearly rallying from a five-run deficit Sunday before falling 9-8.

"Awesome effort by our guys to battle back in the game," Mariners manager Scott Servais said. "... It's just one of those series, and that's how it's going to be for the next week. I don't think a lot went in our favor here. It should flip when we get back home."

Monday's series opener features a heavyweight matchup of right-handers, with Houston's Justin Verlander (11-8, 3.44 ERA) set to go up against Seattle's Luis Castillo (14-7, 3.06).

Verlander, the reigning AL Cy Young Award winner, is 5-3 in nine starts with the Astros since being re-acquired from the New York Mets at the trade deadline. He's 21-10 with a 3.09 ERA in 37 career starts against Seattle.

Castillo has won his past eight decisions, including a 7-2 victory at Oakland last Tuesday when he allowed two runs on five hits over seven innings, with eight strikeouts. Castillo is 2-0 with a 2.70 ERA in three previous starts against the Astros. He beat them 10-1 on July 7 in Houston, allowing one unearned run over seven innings.

"We're still here. We still got a chance and we're here for a reason," Mariners outfielder Julio Rodriguez said. "It's not just luck ... we worked to be here right now. I feel like we've got to just keep on going. At the end, at Day 162, that's when we'll figure it out and see if we're going to go through (to the playoffs) or not. But in the meantime, we've got to keep putting in the effort and keep on going."

The Astros could get a boost from the return of outfielder Michael Brantley, who has missed the past six games with right shoulder soreness. Brantley took batting practice before Sunday's game and might be ready for the series opener in Seattle.