Update: Balfour will have arthroscopic knee surgery Thursday afternoon and is expected to miss four-to-six weeks, according to Susan Slusser of the San Francisco Chronicle.
Recommendation: This is some unfortunate big news for the first week of A's camp. Ryan Cook will likely get the first crack at saves if Balfour is not ready for the start of the season and Sean Doolittle could close out some games if the match-up calls for it.
