Hagadone was placed on the 15-day disabled list on July 8 with a lower-back strain and made his first Minor League rehab appearance on July 15 with Class A (short-season) Mahoning Valley. In that outing, Hagadone faced one batter and threw four pitches before sustaining the season-ending injury.
The injury is similar to the one that A's pitcher Jarrod Parker sustained in May. Dr. Andrews also performed Parker's procedure.
The 29-year-old Hagadone, who underwent Tommy John surgery on the same elbow as a Minor Leaguer in the Red Sox system in 2008, has a 4.