Diego was promoted to Palestino first adult team in 2007 by the coach Luis Musrri, who made debut him against powerhouse team Universidad Católica in a 1–1 draw at Estadio Nacional for the Torneo Clausura.
After a successful season at the team of Calama, reaching the Clausura Tournament semi–finals, in December of that year, he reached an agreement with Universidad Católica for direct to that team in the next season.
Following the departure of Herrera, Reinoso played the first three games of the 2011 Apertura Tournament, until the arrival of the Argentine keeper Alejandro Sánchez against Palestino, Universidad Católica and Cobresal.
The next matchday of the Clausura against Universidad Católica, Renzo netted a twice in a 4–2 away win at San Carlos de Apoquindo Stadium in the 61st minute and in the 90th minute.