 He played in the Club Julio Covarrubias of Padre Hurtado before arriving to Universidad de Chile, with Díaz saying that he felt kind of lucky for being accepted in the club, because he was a very low profile player.He progressed over all categories in the lower divisions, mainly acting as a playmaker.He was promoted to the first team in 2004 at the age of 18, but he was only called to three matches and not debuted in any of them.