Santana was placed on the 15-day injured list with a left ankle sprain Thursday, retroactive to Aug. 3.
Santana hasn't been particularly sharp recently, giving up five runs in 2.1 innings over his last three appearances. It's possible that his ankle injury contributed to his struggles, and he'll be unavailable for at least two weeks. His placement on the IL helps create space on the active roster for Cole Ragans, whose contract was selected Thursday.