In his freshman year, Stephan had a 0–1 win–loss record, 6.57 earned run average (ERA), and 19 strikeouts while pitching 12+1⁄3 total innings.

[5] He posted an 8–1 win–loss record, a 2.88 ERA, five saves, and 88 strikeouts in 68+2⁄3 innings pitched earning NTJCAC first team All-Conference honors.

[18] In 20 games (19 starts) between Trenton and Tampa, he accumulated a 4–7 record and 4.73 ERA with 91 strikeouts across 80 innings.

Stephan did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.

[22] On March 30, 2023, Stephan signed a 4-year major league contract with the Guardians worth $10 million.

He made 71 appearances out of the bullpen for Cleveland, recording a 4.06 ERA with 75 strikeouts and 2 saves across 68+2⁄3 innings pitched.

[24] On March 14, 2024, it was announced that Stephan would undergo Tommy John surgery to repair his UCL, ending his season.