Born in Guayaquil, Mercado agreed to a contract with Athletico Paranaense in July 2019,[1] but only moved to his new side in August 2020, after his 18th birthday.[2] After playing for the under-20s, he impressed manager Alberto Valentim in 2022, and was promoted to the first team squad.[3]
In January 2023, Mercado terminated his contract with Athletico Paranaense and moved to Portugal, joining Liga Portugal 2 side Vilafranquense.[7] At the end of the 2022–23 season, Vilafranquense relocated to Vila das Aves and was rebranded as AVS Futebol SAD.[8] On 18 December 2023, he extended his contract with AVS until 2027.[9]