Holderman was diagnosed with right shoulder discomfort following his appearance in Wednesday's game against Atlanta, Rob Biertempfel of The Athletic reports.
The injury likely explains why Holderman was woefully ineffective Wednesday, as he failed to record an out and was charged with five earned runs on three hits and a walk. The Pirates are labeling Holderman as day-to-day, but a trip to the injured list could be in the forecast if he doesn't show significant improvement heading into the weekend.