Mercado made 22 appearances (18 starts) for the High–A Bowling Green Hot Rods in 2021, recording a 5.35 ERA with 81 strikeouts over 70+2⁄3 innings.[6] He spent 2022 with the Double–A Montgomery Biscuits, compiling a 4–8 record and 4.91 ERA with 115 strikeouts across 24 games (20 starts).[7]
Mercado split the 2023 campaign between Montgomery and the Triple–A Durham Bulls, accumulating a 4.79 ERA with 95 strikeouts and 6 saves over 52 appearances.[8]
Philadelphia Phillies
On November 6, 2023, the Rays traded Mercado to the Philadelphia Phillies, who added him to their 40-man roster.[9] He was optioned to the Triple–A Lehigh Valley IronPigs to begin the 2024 season.[10] Mercado was promoted to the majors for the first time on June 23, replacing the injured Taijuan Walker.[11] He made his major league debut the following day, pitching one scoreless inning.[12]
On June 28, the Phillies announced that Mercado would be assuming Walker's vacant slot in the rotation.[13] On July 2, Mercado made his first start, pitching five innings and earning the win.[14]