 He debuted professionally on 20 March 1937 at Arena Jalisco, in Guadalajara.In his first bout, Delgado drew after ten rounds with fellow Mexican Frankie Zavalza.He won the next match against Isidro Muñoz in the same city, but ended up losing the next three bouts held in Mexico City; first against Carlos Miranda and Jorge Morelia at Arena México, and finally against Luis Argüelles at Arena Coliseo.