KANSAS CITY -- The stage is now set. Luis Castillo made sure of it.

The Mariners’ righty spun six scoreless frames to lead a 2-0 series-clinching victory over the Royals on Thursday afternoon at Kauffman Stadium.

Seattle (84-69) is now tied atop the American League West with idle Houston (84-69) as the two clubs open a crucial three-game set beginning on Friday at Daikin Park that will not only determine the playoff tiebreaker , but could decide the division title as well -- something the Mariners haven’t won since their historic 116-win season in 2001.

After a sudden end to their 10-game winning streak on Wednesday, the Mariners jumped out to an early lead on Thursday thanks to Jorge Polanco’s RBI double in the second inning. Polanco is now batting .370 in September with 11 dou

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