Hicks is one of the hardest throwers in the major leagues, having been measured as throwing as hard as 105 miles per hour (169 km/h).

[2] The St. Louis Cardinals selected Hicks in the third round of the 2015 Major League Baseball draft out of Cypress Creek High School, and he signed with them for $600,000, forgoing his commitment to Tulane.

[5] He was promoted to the Palm Beach Cardinals of the Class A-Advanced Florida State League in July, with whom he was 0–1 with one save and a 1.00 ERA, and 32 strikeouts in 27 innings.

He finished the AFL season with nine appearances, an 0–2 record, and a 6.32 ERA and 16 strikeouts over 15+2⁄3 innings, along with hitting up to 102.6 miles per hour (165.1 km/h).

He made his major league debut against the New York Mets and produced the highest average fastball velocity of the day at 100.4 miles per hour (161.6 km/h).

On April 21, Hicks earned his first major league win when he pitched the final 2+1⁄3 innings—all scoreless—versus the Cincinnati Reds to help seal a 4–3 victory.

[15] Hicks finished his 2018 rookie campaign with a 3–4 record with six saves, a 3.59 ERA, and a 1.34 WHIP, striking out 70 batters in 77+2⁄3 relief innings.

[17] On June 22, 2019, Hicks was removed from a game with elbow irritation and discomfort, and was originally diagnosed with triceps tendinitis.

[34] On July 30, 2023, the Cardinals traded Hicks to the Toronto Blue Jays in exchange for minor league pitchers Adam Kloffenstein and Sem Robberse.

His velocity and overall mechanics began improving, and he continued pitching in the Arizona Fall League after the 2017 season ended, where he regularly threw 100 mph and above.

[41] While starting for the San Francisco Giants, his velocity fell as he worked on preserving his arm over multiple innings, rarely throwing above 96 mph.