Muscles in Matt Harvey's Throwing Shoulder Half the Size of His Other Shoulder Posted Jul 16, 2017 Matt Harvey went on the disabled list on June 15th. The thoracic outlet procedure left Harvey with weakness in the muscles behind his throwing shoulder, which led to problems as he tried to pitch during the first half. Only after Harvey went on the DL did doctors discover that the muscles behind his right shoulder were roughly half the size of those on his left. (The Big Lead)