Gray has been battling the flu recently, which has sapped him of his strength, Derrick Goold of the St. Louis Post-Dispatch reports.

EDGE Analysis

It could help explain why Gray's velocity has been down this spring, though the righty suspects that starting his offseason throwing program later than usual also played a part. Gray said Monday that he's feeling better, and it does not seem as though his availability for Opening Day on Thursday is in question.