Mercado made 15 appearances in the 2018 season, making his debut against the Saint Mary's Gaels in a 6–0 loss on August 24.
[12] Mercado played in both of Des Moines' playoffs matches, but the club was defeated 1–0 by Chicago FC United in the Central Conference Final.
[20][21][22][23] On March 15, 2024, Mercado was announced to be part of Orlando City B's 2024 MLS Next Pro season roster.
[24] On March 16, Mercado made his debut for Orlando City B in the season opener at Atlanta United 2 in a 3–2 victory, playing the full match.
[29] However, on January 30, 2025, Mercado was resigned to the team on a one-year deal with club options for 2026 and 2027 following Mason Stajduhar's departure earlier in the month.