Castillo's (lat) first live bullpen session of spring training concluded early Tuesday after he appeared to experience discomfort, Kevin Acee of The San Diego Union-Tribune reports.
The exact source of Castillo's discomfort isn't known, but he's most likely dealing with a setback related to the left lat/forearm injuries that have sidelined him for the majority of the past two seasons. Despite Castillo's shaky health track record, the Padres recognized enough potential in the reliever to tender him a contract for 2021, hoping he could reemerge as an impact contributor in the middle or late innings. The Padres will presumably evaluate Castillo over the next few days before more information on his latest injury becomes available, but even a minor setback could keep him on the shelf to begin the season.