Castillo has not been present at Rays summer camp for the last four days, Juan Toribio of MLB.com reports.

EDGE Analysis

The reliever was present for the early days of summer camp, even impressing in a live batting practice session Monday. However, Toribio's report implies Castillo's most recent workout was Tuesday, and because teams are prohibited from officially disclosing which players aren't in attendance for workouts, the reason for Castillo's absence remains unknown.