ARLINGTON, Texas—Canelo Alvarez jumped into his trainer’s arms while Billy Joe Saunders slumped in his corner with a towel draped over his head. The wildly popular Mexican fighter added another super middleweight title belt in front of a huge crowd in another fight in Texas. Not only did Saunders have his first loss as a pro, the English fighter might have a broken eye socket. Alvarez set up another victory in his latest Cinco de Mayo bout with a staggering right hand in the middle of the eighth round, sending 73,126 already-screaming fans at the home of the Dallas Cowboys into a frenzy as we waved his arms to encourage the noise while the round continued. Saunders’ corner waved in defeat before the ninth while treating a cut under his right eye. Alvarez (56–1–2, 38 knockouts) added Saunders’ WBO belt to his WBA and WBC straps in his third fight …