Mauricio has fought many undefeated boxers, including Shane Mosley, Dingaan Thobela, Todd Foster, Dennis Holbæk Pedersen, Billy Schwer and Rene Arredondo. WBO Lightweight Championship
He had to survive cuts over both eyes. One of his last fights was a loss to boxing legend Jorge Páez.
He was the first ever WBO Lightweight Champion. Aceves won the WBO Lightweight Championship by upsetting the veteran Amancio Castro in Santa Ana, California. He almost lost his championship in his first defense, when his opponent Bejines had won every round before being knocked out with a single short left hook by Mauricio.
