He's arguably boxing's biggest star now, yet even as he prepares to fight Miguel Cotto on Saturday at the Mandalay Bay Events Center in a hotly anticipated bout that will be distributed by HBO Pay-Per-View, he's haunted by memories of his worst night as a pro. Twenty-six months ago, a bold, confident and unbeaten Alvarez climbed into the ring convinced that he'd topple Floyd Mayweather Jr. Mayweather entered that bout as boxing's reigning pound-for-pound champion. But Alvarez, 23 at the time, scoffed at the notion that after eight years and 43 fights he was in over his head.