[2] He made his professional debut with the rookie–level Johnson City Cardinals, pitching to a 5.52 ERA across 13 contests.
[5] In 2021, Leahy appeared in 25 games and struggling to an 0–8 record and 8.20 ERA with 63 strikeouts across 86+2⁄3 innings pitched.
[6] In 2022, Leahy spent time with Springfield for a third season, also appearing in one game for the Triple–A Memphis Redbirds.
[9] In 3 games for St. Louis, he allowed four runs on four hits and five walks with two strikeouts in 1+2⁄3 innings pitched.
[10] On April 30, 2024, the Cardinals selected Leahy's contract, adding him back to the major league roster.