The Mariners could remove Castillo from the rotation when Bryce Miller (oblique) returns next week, Adam Jude of The Seattle Times reports.
It's just one option the team is mulling, as Miller and Emerson Hancock are also being considered for the bullpen or piggyback roles. It would be an easy decision to bump Castillo from the rotation if it were based purely on performance, as he's posted a 6.29 ERA, 1.66 WHIP and 31:13 K:BB over 34.1 innings in his first seven starts. However, Castillo has never pitched in relief at the major-league level, while Miller and Hancock both have. A six-man rotation is also under consideration. Castillo will start Saturday in Chicago against the White Sox in what could be his final opportunity to convince the Mariners he should remain in the rotation.