New York Yankees The
New York Yankees selected Diehl in the 27th round of the
2016 MLB draft. He signed with the Yankees for $50,000 rather than return to college, and was assigned to the
Staten Island Yankees of the
Low–A New York-Penn League. He began the 2018 season with the
Tampa Tarpons of the
High–A Florida State League and was promoted to the
Trenton Thunder of the
Double–A Eastern League.
Colorado Rockies On March 23, 2019, the Yankees traded Diehl to the
Colorado Rockies in exchange for outfielder
Mike Tauchman. After the trade, he played for the
Hartford Yard Goats, and the
Albuquerque Isotopes. On June 10, 2019, his contract was selected and he was called up to the major leagues for the first time. He made his debut on June 11 versus the
Chicago Cubs, allowing two runs in one inning of relief. On June 23, 2020, it was announced that Diehl had tested positive for
COVID-19. He returned in time for the start of summer camp on July 4. In 2020, Diehl pitched six innings in as many games, allowing seven runs on seven hits for a 10.50 ERA with four strikeouts. On April 10, 2021, Diehl was designated for assignment after
Alan Trejo was added to the roster.
Cincinnati Reds On April 14, 2021, Diehl was claimed off waivers by the
Cincinnati Reds. On May 2, 2021, Diehl was designated for assignment by Cincinnati following the waiver claim of
Ashton Goudeau. On May 4, Diehl was outrighted to the Triple-A
Louisville Bats. Diehl was assigned to Triple-A Louisville to begin the 2022 season. He recorded a 4.50 ERA and 0.75 WHIP in eight innings of work across eight relief appearances before he had his contract selected to Cincinnati's active roster on April 27, 2022. On May 9, Diehl was designated for assignment by Cincinnati. On May 12, he cleared waivers and was sent outright to Triple-A Louisville.
New York Mets On July 28, 2022, the Reds traded Diehl and
Tyler Naquin to the
New York Mets for minor league prospects Jose Acuña and
Héctor Rodríguez. Diehl made 13 appearances for the Triple-A
Syracuse Mets to close out the year, but struggled to an 0–2 record and 8.27 ERA with nine strikeouts in innings pitched. He elected free agency on October 9, 2022.
Cleveland Guardians On February 7, 2023, Diehl signed a minor league contract with the
Cleveland Guardians organization. In 24 games for the Triple–A
Columbus Clippers, he struggled to a 6.89 ERA with 35 strikeouts in innings pitched. On August 16, Diehl was released by Cleveland.
Lancaster Stormers On June 4, 2024, Diehl signed with the
Lancaster Stormers of the
Atlantic League of Professional Baseball. In 41 games for Lancaster, he compiled a 4–3 record and 2.29 ERA with 50 strikeouts and 3 saves across innings pitched. On March 28, 2025, Diehl re-signed with the Stormers for a second season. In 52 games 55.1 innings of relief he went 3-4 with a 3.74 ERA with 63 strikeouts and 7 saves. ==References==