Reds general manager Dick Williams said Monday that DeSclafani will be shut down for up to a month. An MRI done in Cincinnati revealed a sprained right ulnar collateral ligament.
"It will certainly impact his ability to start the season on the active roster," Williams said. "I anticipate him opening the season on the disabled list. We will be working with him when he returns to Arizona to get a treatment plan in place."
DeSclafani missed the start of the season last year with a strained left oblique. The 26-year-old righty returned to post a 9-5 record in 20 starts.
Reds pitcher Homer Bailey had bone chips removed on Feb. 8, leaving two open spots in the rotation.