The Angels announced the nature of the 19-year-old Adell's unusual injury combination Sunday.
Adell hurt himself when he slipped on the bag while rounding second base during a split-squad exhibition game against the Cubs in Mesa.
The slugging outfielder is batting .391 in spring training with the Angels. He was expected to start the season with Double-A Mobile on his fast track toward the majors.
Adell is ranked the sixth-best prospect in the sport by Baseball America. The Angels chose him with the 10th overall pick in 2017.