In 2016, Cox's freshman year at Mercer, he pitched 24 innings, compiling a 2–2 record and a 10.13 ERA. As a sophomore in 2016, he started 15 games, going 4–2 with a 5.69 ERA.[3] In 2018, his junior season, he was named Mercer's Friday night starter.[4] Over 17 starts, Cox pitched to a 7–4 record with a 4.52 ERA, striking out 124 batters over 87+2⁄3 innings.[5]
To begin the 2021 season, he was assigned to the Northwest Arkansas Naturals of the Double-A Central, and was promoted to the Omaha Storm Chasers of the Triple-A East in late September.[14] Over 17 games (16 starts) between the two clubs, Cox went 4-1 with a 4.10 ERA and 56 strikeouts over 63 innings.[15][16] He returned to Omaha for the 2022 season.[17] Over 29 games (24 starts), he went 7-7 with a 4.21 ERA and 105 strikeouts over 147+1⁄3 innings.[18] Cox began the 2023 season with Omaha, posting a 2.21 ERA, 22 strikeouts, and 11 walks in 20+1⁄3 innings pitched across five games (four starts).
On May 3, 2023, Cox was selected to the 40-man roster and promoted to the major leagues for the first time.[19] He proceeded to set a modern Major League Baseball record by not allowing a hit to any of the first 39 batters he faced.[20] In 24 appearances for Kansas City, Cox logged a 4.54 ERA with 33 strikeouts in 35+2⁄3 innings pitched. On September 8, Cox departed an outing against the Toronto Blue Jays after he was struck by an Alejandro Kirk come backer and collapsed in pain as he tried to cover first base.[21] The next day, he was placed on the 60–day injured list, ending his season.[22] On September 12, Cox was diagnosed with a full ACL tear in his left knee, as well as damage to his MCL in the same knee.[23] On November 17, Cox was designated for assignment by the Royals following the acquisition of Nick Anderson.[24] The following day, Kansas City re-signed him to a minor league contract.[25]
Cox spent the 2024 campaign with Triple–A Omaha, compiling a 3.90 ERA with 31 strikeouts across 30 innings pitched. On July 11, 2024, Cox opted out of his minor league contract and elected free agency.[26] Cox re–signed with the Royals on a new minor league contract on July 16.[27] On November 6, he elected free agency.[28]
^Battifarano, Andrew (September 13, 2019). "Cox hurls gem, keeps Blue Rocks alive". MiLB.com. Retrieved September 17, 2024. ...after [Cox] was promoted from Class A Lexington on June 23.