Santos then vacated the WBO title to go up in weight and pursue the WBO Light Middleweight Championship and Margarito was assigned to fight Antonio Díaz for the vacant title in front of an HBO Boxing audience. On March 16, 2002, Margarito crowned himself world champion, beating Diaz by knockout in round ten. He defended that crown with a decision in twelve over Danny Perez Ramírez and a knockout in two over former WBA title holder Andrew Lewis. Lewis was a southpaw and a hard puncher, but had been exposed as having a weak chin, while Margarito proved that he has a world class chin. He publicly asked for a unification bout with then WBC and WBA Champion Ricardo Mayorga.