The White Sox announced that John Danks will not be returning this season and will be undergoing exploratory surgery on his left shoulder on August 6. Danks has not pitched in the majors since May 19.
After signing a 5 year, $65 million contract during the offseason, Danks was expected to help anchor the White Sox starting staff. Instead, Danks pitched poorly prior to being placed on the disabled list: 9 GS, 53.2 IP, 57 H, 23 BB and 30 K, resulting in a 3-4 record and a 5.70 ERA.
In the past few months, he's twice attempted throwing programs in order to return this season. His first attempt ended after a rehab start at Triple-A Charlotte on June 12, after which a subsequent MRI showed he had a Grade 1 subscapularis muscle tear in his left shoulder. His most recent attempt did not go past some light throwing sessions.
With the addition of Francisco Liriano, the White Sox now have six recognized starting pitchers and Liriano's acquisition presumably was made in part with the expectation that Danks would not be able to return this season.
The 27 year old left-hander is in his sixth season with the White Sox. He's compiled a 57-60 record with a 4.12 ERA. He has been worth 18.3 bWAR and 16.6 fWAR.
"Exploratory surgery" usually indicates that testing, including imaging as well as physical tests, are inconclusive as to what the problem is (or what the extent of the problem is). If a problem is found during the surgery (such as a tear in his labrum) the surgeon will go ahead and fix the issue during the same surgery. When he would be able to pitch again is dependent upon what is found during the surgery. Best case scenario would be a spring training return; however, that is unlikely and it is more likely that Danks would be out for at least a year from the date of the surgery.