Early on in his NBA career, Roy was already a three-time All-Star within his first four seasons. Indeed, he seemed set to achieve impossibly great heights. Unfortunately, complications with his knees forced this budding superstar to retire - twice. You heard us. After undergoing an operation to remove a piece of cartilage in his left knee, he subsequently retired after finding difficulty playing during the 2010/11 season. He attempted a comeback in Minnesota in the 2012 season. It lasted just 5 games before he required yet another operation, this time in his right knee. He then retired for good.