Mariners general manager Justin Hollander said Tuesday that Castillo will work in relief behind starter Bryce Miller during Friday's game against the Red Sox as part of a piggyback arrangement, Adam Jude of The Seattle Times reports.
Castillo and Miller made standalone starts in both of their last two appearances, but the two will shift back into a tandem setup Friday. They previously worked in a piggyback arrangement on three occasions back in May, with Miller covering between five and 5.2 frames in those games and Castillo ranging between 2.1 and five innings. According to Hollander, the Mariners plan to condense their rotation to five through the All-Star break, with all six of their starters rotating through and being part of at least one piggyback game over the next month. Hollander noted that it was merely a coincidence that the new staff-wide piggyback plan is beginning with Miller and Castillo, so both are expected to be separated and make traditional starts when their turn in the pitching schedule comes up again next week.