Although Joey Mercury certainly suffered one of the most visually gruesome injuries in WWE history, it wasn't directly responsible for cutting off his career at the legs. As part of MNM (with Johnny Nitro and Melina), he was on the receiving end of a stray ladder in a match against the Hardys. He suffered a broken orbital bone and nose, requiring over 30 facial stitches and a few weeks on the sildelines. The incident took a far longer toll on Mercury however, as he became addicted to the painkillers prescribed to him. This was particularly destructive for Joey, previously a drug addict, and Vince McMahon was forced to release him from his contract until he cleaned himself up. Fortunately for Joey, he has managed to turn his life around, and enjoys a minor onscreen role as one of Seth Rollins' lackeys alongside Jamie Noble - a rare case of an injury eventually leading to a happy ending.
