On November 22, 2003, Díaz won the WBO youth lightweight title with a sixth-round TKO of journeyman Joel Pérez [REF].
On April 28, 2007, Diaz was upgraded to super champion by the WBA, successfully defending his title against WBO champion Acelino Freitas by TKO after Freitas forfeited the fight before beginning the 9th round, unifying the WBO lightweight championship with the WBA (Super) lightweight title.