Kerr signed with the Seattle Mariners of Major League Baseball as an undraftedfree agent on August 24, 2017.[1] He made his professional debut with the Single-A Clinton LumberKings in 2018, logging a 5–11 record and 4.28 ERA with 101 strikeouts across 25 starts. In 2019, Kerr split the season between the High-A Modesto Nuts and the Triple-A Tacoma Rainiers, posting a 4–7 record and 3.82 ERA with 95 strikeouts in 92.0 innings of work across 36 total appearances. Kerr did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.[4] He split the 2021 campaign between the Double-A Arkansas Travelers and Tacoma, pitching to a 3.18 ERA with 60 strikeouts in 36 appearances. The Mariners added him to their 40-man roster to protect him from the Rule 5 draft following the season on November 19, 2021.[5]
San Diego Padres
On November 27, 2021, the Mariners traded Kerr and outfielder Corey Rosier to the San Diego Padres in exchange for Adam Frazier.[6] He was assigned to the Triple-A El Paso Chihuahuas to begin the 2022 season.
On April 22, 2022, Kerr was promoted to major leagues for the first time to replace the injured Pierce Johnson.[7] He made his major league debut on April 24.[8] He appeared in seven games for San Diego in his rookie campaign, pitching to a 9.00 ERA with three strikeouts in five innings pitched.
Kerr was optioned to Triple-A El Paso to begin the 2023 season.[9]
Atlanta Braves
On December 15, 2023, the Padres traded Kerr, Matt Carpenter, and cash considerations to the Atlanta Braves in exchange for Drew Campbell.[10][11] He was optioned to the Triple–A Gwinnett Stripers to begin the 2024 season.[12] On May 7, 2024, Kerr was selected to the active roster following an injury to Tyler Matzek.[13] On May 24, Kerr made his first career start against the Pittsburgh Pirates.[14] In 10 games, he recorded a 5.64 ERA with 27 strikeouts across 22+1⁄3 innings pitched. On June 24, it was announced that Kerr would require Tommy John surgery, ending his season.[15][16] On November 22, the Braves non–tendered Kerr, making him a free agent.[17]
On November 26, 2024, Kerr re–signed with the Braves on a minor league contract.[18]