The surgery was performed by Dr. Douglas Freedberg at the Surgcenter at Pima Crossing.
Balfour, 35, saved a team-high 24 games in posting a 3-2 record and 2.53 ERA in 75 relief appearances last year. He was charged with only two blown saves for the 2012 American League West Champions, with his .923 save percentage (24 of 26) ranking fourth in the American League and tied for fourth best in Oakland history.
The Sydney, Australia native also ranked second among AL relievers in opponents' batting average (.160), third in slugging percentage (.253), fourth in on-base percentage (.242), fifth in games (75) and tied for fifth in innings (74.2). Dating back to Sept. 22, Balfour has retired the last 26 consecutive batters he's faced—tied for the fifth longest streak in Oakland history.