Castillo cleared waivers and was outrighted to Triple-A Toledo on Thursday.
Castillo appeared in three games for the Tigers in 2022, so it's not a major surprise he won't remain on the 40-man roster through the offseason. He spent most of the year at Toledo, where he had a 1.74 ERA, 1.22 WHIP and 39:11 K:BB over 41.1 innings.