He was part of the Uruguay squad for the 2010 World Cup and one year later, he won the 2011 Copa América, earning him his first international honour, despite not making an appearance in the competition.?

Castillo began his football career at the local amateur club Santa Bernardina of his natal city Durazno, in where he played in the youth ranks of the team during 1989 to 1997.

After a very good spell in the club, for example his nomination to the national team squad for the 2007 Copa América celebrated in Venezuela, among his achievements, in December 2007, was confirmed his move to Brazilian side Botafogo.

[9] Castillo become of good form the Campeonato Carioca, saving a penalty to Victor Hugo of Friburguense in the 4–1 win of Botafogo,[10] in the first official game of "The wall" for that tournament.

On 10 May 2008, he made his league debut for Botafogo against Cruzeiro for the second week of the Campeonato Brasileirão, in where the club suffered a 1–0 away defeat at Mineirão Stadium with a goal of Guilherme in the 11th minute.

Of this form he returned to the titularity in Botafogo's goal after of challenge the post with Renan during weeks ago,[14] receiving also a call-up from his national team for dispute the 2010 World Cup Qualifiers against Brazil and Venezuela.

[15] He started several games consecutive with the coach Ney Franco until his dismissal, but with the arrival of Estevam Soares he preferred to Jéferson in the goal and Castillo again was relegated to the bench.

[21] However the next game Castillo had a better performance against Millonarios which Cali won 4–1[22][23] and then began to reach a well level that allowed him be nominated in the 23-man Uruguayan squad to face the 2010 FIFA World Cup at South Africa.

[24] Following Uruguay's successful World Cup at Africa where they finished in the fourth place, Castillo returned to Cali to face the Torneo Finalización where Los Azucareros failed to qualify the playoffs to contest the league title.

[33] On 26 January, during the Noche Alba (Colo-Colo's last pre-season game where presents their signings) he produced a man of the match performance in a 3–2 defeat to Nacional, so that won the recognition from the press and the fans despite the loss.

[35][36] However, on 3 February, Castillo suffered a two weeks injury which he missed the Torneo Apertura second matchday game against Santiago Wanderers[37] that Colo-Colo lost 2–1 with Raúl Olivares in the goal.

[45] Finally Colo-Colo won 3–0 to Palestino during Pérez's last caretaking match where Castillo had casual crash with Arab team striker Nicolás Canales which the Uruguayan publicly apologized him in front of the press and then via Twitter.

On 2 March 2011, Castillo played in Gallego's first match in the bench that Colo-Colo won 4–2 to Venezuelan Deportivo Táchira for the Libertadores where receive a twice of the Chilean Julio Gutiérrez.

[citation needed] The club continued his rise after winning 2–1 to Unión Española at Santa Laura on 6 March where his performance was marred after receiving a 20-yard goal of Kevin Harbottle who chipped Castillo.

Following the Uruguayan's relegation, he returned in the 2–1 Libertadores win over Táchira[50] for then play in the derby against Universidad Católica on 20 April which was 1–1 draw where receive another free-kick goal, now from Juan Eluchans.

On 18 June, once finished the Apertura was reported that Gallego would studying the possibility of Castillo's disappointing of the club to use his foreign bid in a midfielder to face the Torneo Clausura.

In June 2010, Castillo was named in the 23-man squad of Uruguay for the 2010 FIFA World Cup in South Africa as the second choice goalkeeper behind Fernando Muslera and before Martín Silva.