Richardson signed with the Reds and made his professional debut that year with the Greeneville Reds of the Rookie-levelAppalachian League.[9] Over 29 innings, he compiled a 0–5 record and a 7.14 ERA.[10] In 2019, his first full minor league season, he played with the Dayton Dragons of the Single-AMidwest League, going 3–9 with a 4.15 ERA and a 1.41 WHIP over 26 starts.[11] After the cancellation of the 2020 minor league season due to the COVID-19 pandemic, he flew to Palm Beach Gardens, Florida, and spent the summer working out at Cressey Sports Performance, participating in simulated games with fellow minor leaguers.[12] In September, he was added to Cincinnati's 60-man player pool and participated in their instructional league.[13] Richardson was assigned to Dayton, now members of the High-A Central, for the 2021 season; he appeared in 19 games (18 starts) in which he went 2–5 with a 5.09 ERA, 91 strikeouts, and 38 walks over 76 innings.[14] Following the season's end, he underwent Tommy John surgery, and thus missed all of the 2022 season.[15]
On November 15, 2022, the Reds selected Richardson's contract and added him to the 40-man roster.[16] Richardson split minor league time in 2023 between the Daytona Tortugas, the Chattanooga Lookouts, and the Louisville Bats.[17] On August 6, Richardson was called up to the major leagues for the first time to make his MLB debut.[18] He made 4 starts for the Reds, struggling to an 8.64 ERA with 13 strikeouts across 16+2⁄3 innings pitched.
Richardson was optioned to Triple–A Louisville to begin the 2024 season.[19] He made one appearance for Cincinnati, allowing two runs on two hits with one strikeout in 2⁄3 of an inning pitched against the Chicago Cubs.
Richardson was again optioned to Triple-A Louisville to begin the 2025 season.[20] He made 34 appearances for Cincinnati during the regular season, posting an 0-3 record and 4.54 ERA with 30 strikeouts across 37+2⁄3 innings pitched. On December 27, 2025, Richardson was designated for assignment following the acquisition of Dane Myers.[21] He cleared waivers and was sent outright to Louisville on January 7, 2026.[22]
