Castillo left Thursday's game against the Rockies due to an apparent finger injury, Kevin Acee of The San Diego Union-Tribune reports. He walked one and struck out two over 0.2 innings prior to departing.
Castillo was just activated from the injured list earlier in the day after missing time with a left forearm flexor strain, though he now appears to be dealing with a blister on his right hand, per Acee. The lefty will be considered day-to-day until more information on his status is revealed.