It's always a little sad to watch a great pitcher struggle with arm troubles. That means that Chris Carpenter's career has been a Shakespearean tragedy. He's missed major amounts of time with arm trouble and just when he seemed to be hitting his stride after a Cy Young Award in 2005 and a solid year in 2006, he needed Tommy John surgery and the complications forced him to miss all of 2007 and almost all of 2008. Now, things appear to be even worse.
Further examination into his arm after his slow recovery from the TJ has shown that there is scarring on the nerves in his right shoulder and the St. Louis Post-Dispatch says a source close to the pitcher calls it "a big deal," acknowledging that he might not ever pitch again. Currently, doctors are debating a way to alleviate the pain that the scarring is causing, possibly by surgery.
The root of the nerve problem here is also what caused Carpenter's problems in 2004 and it seems to be a fairly unique condition. No one's saying anything yet about Carp's future, but surgery's no bet to alleviate the problem and even if it does, he'd have a long road back to rehab from yet another arm surgery.