Smith-Shawver will either undergo Tommy John surgery or an internal brace procedure.
He left Thursday's game against the Philadelphia Phillies in the second inning after he felt a "pop" in his throwing arm.
Smith-Shawver had been throwing a solid 3.86 ERA (earned run average) this season through nine starts, posting 42 strikeouts and 42 hits through 44.1 innings.
Earlier this month, he even took a no-hitter into the eighth inning in a start against the Cincinnati Reds, the longest outing of his career.
He finished the game giving up just one hit while walking four and striking out five.
The young stud was finally hitting his stride in the majors, but it came to an unfortunate end.