Washington Nationals Cronin was a reliever at the
University of Arkansas in all 65 of his appearances in his
collegiate career. The
Washington Nationals drafted him in the fourth round of the
2019 Major League Baseball draft, and after he signed with Washington, he was assigned to the High-A
Hagerstown Suns for the remainder of the 2019 season. He had a 0.82 ERA in his first professional season, striking out 41 batters in 22 innings. He was named to the Nationals' player pool during the
COVID-19 pandemic–shortened
2020 season, although he was not called up to the major leagues. Before the
2021 season, Cronin ranked as the organization's ninth-best prospect, according to
Baseball America. The Nationals invited him to participate in major league spring training in 2021. After spring training, Cronin was assigned to the High-A
Wilmington Blue Rocks to begin the 2021 season, although
MLB Pipeline speculated that he could rise quickly in a relief role. In 2022, Cronin split the year between the Double-A
Harrisburg Senators and Triple-A
Rochester Red Wings. In 48 relief appearances, he had a combined 2.42 ERA with 56 strikeouts in 52 innings of work. On November 15, 2022, the Nationals added Cronin to their
40-man roster to protect him from the
Rule 5 draft. Cronin was optioned to Rochester to begin the 2023 season. In 14 games, he logged a 5.02 ERA with 13 strikeouts across innings pitched. On August 2, 2023, it was announced that Cronin would undergo season-ending surgery to repair a
herniated disc in his back. Following the season on November 6, Cronin was
designated for assignment after multiple players were activated from the injured list. He cleared waivers and was sent outright to Triple-A Rochester on November 10. Cronin split the 2024 campaign with Harrisburg and Wilmington. He made 40 combined appearances out of the
bullpen, registering a 1.42 ERA with 54 strikeouts and 10
saves across innings pitched. After the season, he pitched for the Salt River Rafters in the
Arizona Fall League.
Seattle Mariners On December 11, 2024, the
Seattle Mariners selected Cronin with the 61st overall pick of the minor league phase of the
Rule 5 draft. He began the 2025 season with the Double-A
Arkansas Travelers. In 15 total appearances split between Arkansas and the Triple-A
Tacoma Rainiers, he logged a 2-0 record and 0.86 ERA with 21 strikeouts over 21 innings of work. Cronin elected free agency following the season on November 6. ==Pitching style==