On 30 January 2011, he officially debuted in a 2–2 home draw with Cobresal receiving goals from Víctor Osorio and Héctor Pericás. However, on 3 February, Castillo suffered a two weeks injury which he missed the Torneo Apertura second matchday game against Santiago Wanderers that Colo-Colo lost 2–1 with Raúl Olivares in the goal. Not obstant, in his return to Colo-Colo's goal on 18 February he had a poor performance in a 5–1 home loss to Universidad de Concepción that meant the biggest home defeat in the club's history and the worst start of championship since 1989 selling Cagna's firing.