HOUSTON -- The standard of expectation is so high for the Houston Astros, reigning World Series champions and possessors of the second-best record in baseball, that any unusually poor performance subsequently demands a lengthy explanation from all the involved parties.

On Wednesday, the Astros (95-67) closed their season series against the Seattle Mariners with a thud, suffering a 9-0 loss that matched their largest defeat by margin on the season. Houston suffered a pair of nine-run setbacks in the span of six days in late July and are a robust 35-8 in blowouts (games decided by five or more runs) this season. Yet, with a postseason berth nearly clinched and the hard-charging Oakland Athletics in dogged pursuit for the American League West title and the No. 2 seed in the playoff picture, the timing of the performance troubled.

"September baseball," said Astros manager A.J. Hinch, whose club is 13-4 this month. "I know that's kind of a thing this year where everybody is using a lot of pitchers. It's a lot easier to do it in September. It's a challenge. It's no different than when you run into a spot starter, you run into a game where they can utilize their whole bullpen depending on their schedule."