Born in
Guayaquil, Mercado joined Academía Alfaro Moreno in 2005, aged ten. In 2011, he moved to giants
LDU Quito, initially assigned to the youth setup. On 11 August 2012, Mercado played his first match as a professional, coming on as a second-half
substitute in a 0–0 away draw against
Técnico Universitario, for the
Ecuadorian Serie A championship. He scored his first professional goal on 12 May of the following year, netting his side's only in a 1–1 home draw against
LDU Loja. On 25 July 2014, Mercado and teammate
Gabriel Corozo joined
Granada CF, being assigned to
the reserves in
Segunda División B. On 13 February of the following year he was loaned to
Godoy Cruz, until December. On 7 December 2015, it was confirmed, that Mercado had signed a loan deal with
CA Sarmiento, short after his return from another loan move. On 2 February 2017 his loan to Sarmiento was ended and he was sent on loan to Bulgarian club
CSKA Sofia for 1 year. ==Career statistics==