Glasnow left Saturday's game in the fourth inning with right shoulder discomfort.
He was erratic when on the mound, walking three batters and hitting two others with just 42 of his 78 pitches going for strikes. The Pirates figure to put Glasnow through a battery of tests to determine the full extent of the issue, as they won't want to take any chances with one of their top prospects. Ryan Vogelsong (eye) could be ready to fill a rotation spot soon.