HOUSTON -- Houston Astros left-hander Dallas Keuchel did what was required of an ace on Saturday, working six strong innings to put his club in position to win before delivering a comfortable lead to his bullpen. What reliever Joe Musgrove did subsequently was equally vital to the Astros' success.

After Keuchel cruised, Musgrove put out a raging fire in the eighth inning and the Astros defeated the Seattle Mariners 8-6 at Minute Maid Park, reducing their magic number to win the American League West to one.

The Astros had an opportunity to clinch the title after they left the ballpark but the Los Angeles Angels defeated the Texas Rangers to remain alive.

Keuchel (13-4) faced one batter over the minimum through four innings, induced an inning-ending double play to escape trouble in the fifth and, after surrendering a leadoff home run to Seattle shortstop Jean Segura in the sixth, closed that frame with three consecutive strikeouts.

The Astros (90-58) reached 90 victories in a season for the first time since 2004, a benchmark that dovetails with their steady ascension from cellar dwellers to pending division champions.

"It's going to be a culmination of a lot of lean years and I'm the product of getting a couple of opportunities and I'm really appreciative of that and I always will be," Keuchel said of the prospect of winning the AL West. "Nobody wants to lose, and now that we've established a winning culture here it's hopefully the first of many AL West titles and deep playoff runs."

In defeating the Mariners (74-75) for the third time in as many starts this season, Keuchel allowed one run on four hits and two walks with four strikeouts. His won-loss ledger received an assist from Musgrove, who inherited two runners with no outs after Astros right-hander Francis Martes surrendered four runs without retiring any of the five batters he faced.

With the tying run on base, Musgrove recorded a pair of strikeouts before getting Seattle catcher Carlos Ruiz to pop out to shortstop Carlos Correa. Musgrove returned in the ninth and recorded his first career save despite allowing a two-out homer to right fielder Mitch Haniger.

"Pretty awesome to come in the way that he did," Astros manager A.J. Hinch said of Musgrove. "There were a lot of restrictions on the bullpen today, so when you have that you need guys to step up and come in and close the door. ... Joe Musgrove steps up and threw exceptionally well. He's really taken to the bullpen role. Today was a good example."

Derek Fisher and George Springer posted two-out hits against Mariners right-hander Erasmo Ramirez (5-6) in the second inning, lifting the Astros to a 4-0 lead. Houston chased Ramirez in the fifth by scoring two additional runs, with Carlos Beltran plating Jose Altuve with a single.

"He's had that happen a couple of times where he's fallen off the rails a little bit," Seattle manager Scott Servais said of Ramirez, who had worked at least six innings while not allowing more than three runs over his previous six starts. "Just command and stuff wasn't sharp in the second inning.

"I thought he hung in there. It obviously wasn't his best outing he's had with us. Walked a few guys more than normal. Got some balls up in the zone and wasn't able to work his way through their lineup. Thought his ball had a lot of good movement today, not the exact location we've seen out of him in the past."

Beltran finished 3-for-4 with a double and a pair of RBIs. Fisher, Springer and Altuve each recorded two hits as did right fielder Josh Reddick, who went 2-for-4 with a walk and two RBIs.

Houston tacked on runs in the seventh and eighth to keep the Mariners at bay and put another dent in their postseason hopes. But the second inning produced the most damage.

"It was kind of tough that inning but after that the rest was trying to work my command and attack the hitters," Ramirez said. "It was something that didn't happen today.

"Season isn't over yet and we still have more games to go. Have to be ready for the next one."

NOTES: Mariners RHP Felix Hernandez and LHP James Paxton will take their normal turns in the Seattle rotation next week, following RHP Mike Leake while pitching Wednesday and Thursday, respectively, against the Texas Rangers. Hernandez and Paxton were reinstated from the disabled list on Thursday and Friday. ... Astros RHP Collin McHugh was in the bullpen but did not pitch for a second consecutive day. His status as a starter remains tied to the availability of RHP Lance McCullers, who is tentatively scheduled to start on Tuesday. ... Mariners LHP Ariel Miranda made his first relief appearance of the season and the fifth of his career when he entered to open the sixth inning. Miranda led Seattle pitchers in starts (29) and innings (158).