Carpenter last pitched in relief at Arizona on Sept. 2. Carpenter, who missed almost all of 2007 after undergoing Tommy John surgery, didn't make his season debut until July 30. The 2005 Cy Young Award winner finished 0-1 with a 1.76 ERA in four appearances, making three starts.
The additional tests on Carpenter's shoulder revealed nerve irritation, which has hampered his ability to recover after each appearance. The team said in a statement it was optimistic Carpenter would return in 2009.
Also Friday, the team announced that reliever Jason Isringhausen had surgery to repair the torn tendon is his right elbow. Outfielder Rick Ankiel, who has missed time with an abdominal injury, met with a specialist in Philadelphia and is likely to have surgery soon.
Nats RHP Hill to have arthroscopic elbow surgery
La Liga Preview: Espanyol - Valladolid
Cardinals closer Isringhausen to undergo surgery
