Matthew Riddle (7-3 MMA) announced his retirement from mixed martial arts on Monday night. The 27-year-old, Riddle, was slated to fight Luis Melo (29-11 MMA) at next weeks Bellator 100 event, which features the opening round of the promotions Season 9 welterweight tournament. However,  Riddle apparently suffered a cracked rib in training and thus has decided […]