Nietes, 30, clung to the belt after a bruising encounter with the Mexican and there may well be calls for a rematch between the two after the judges came back with scores of 114-114 (twice) and 115-113 to the Filipino.
On the undercard, 21 year-old Genesis Servania pushed his unbeaten run to 19-0 with a crushing seventh round stoppage win over former world title challenger Angky Angkotta.