The righty was designated for assignment before the holidays but lingered in DFA limbo for a while since the normal seven-day window is paused between Christmas and New Year’s. Boston’s 40-man roster is now at 40, though their deal with Lucas Giolito has not yet been made official.

Castillo, 25 in May, has 59 2/3 innings of major league experience to this point in his career. He has a 5.43 earned run average in that time, having stuck out 18.1% of batters faced, walked 9.3% and kept 44.7% of balls in play on the ground.