Segundo Alejandro Castillo Nazareno (born 15 May 1982) is an Ecuadorian football coach and former player who played as a midfielder.

Born in San Lorenzo, Esmeraldas, Castillo started his career with Quito's Club Deportivo Espoli spending three years with the team, scoring a decent 11 goals in 66 appearances.

He scored his only goal for the Toffees on his home debut against Standard Liège on 18 September 2008 in a UEFA Cup tie with a powerful volley from 25 yards out.

[6] Castillo returned to the Premier League once again when he joined newly promoted Wolverhampton Wanderers on a season-long loan on 31 August 2009.

[9][10] On 4 December 2014, it was announced by Dorados de Sinaloa that Castillo would be joining their roster for the next season of the Ascenso MX.

Castillo was left out of the 2014 World Cup during a friendly match with Mexico due to a horrific collision with Luis Montes.