Renowned orthopedist Dr. Lewis Yocum confirmed the tear while examining the MRI taken on Klein's shoulder last week in Baltimore.
The Orioles believe that Klein can rehab the shoulder and avoid surgery, as Jason Berken and former Oriole Matt Albers have done.
Klein will report to the minor league complex in Sarasota, Fla., on Monday, but it's not known when he'll begin his rehab and how long it will last. It could be anywhere from four to eight weeks. It's difficult to pinpoint right now.
The Orioles wanted to promote Klein to Triple-A Norfolk, but those plans have been shelved. He's a combined 3-1 with a 1.11 ERA between Single-A Frederick and Double-A Bowie, with six walks and 37 strikeouts in 32 1/3 innings.