Smith-Shawver was diagnosed with a Grade 2 left oblique strain Friday, Justin Toscano of The Atlanta Journal-Constitution reports.
Smith-Shawver was placed on the 15-day injured list earlier Friday, though a Grade 2 strain likely means a six-to-eight-week recovery timeline. The 21-year-old righty was called up Thursday to make a spot start against the Cubs, and Atlanta's pitching needs will likely dictate whether he remains in Atlanta or heads to Triple-A Gwinnett once he returns from the IL -- likely sometime in July.