[6] The Seattle Mariners selected Miller in the fourth round with the 113th overall pick of the 2021 Major League Baseball draft.
[9] In 2022, Miller made 27 appearances (26 starts) split between Modesto, the High-A Everett AquaSox, and the Double-A Arkansas Travelers, posting a combined 7–4 record and 3.16 ERA with 163 strikeouts in 133+2⁄3 innings pitched.
[10] Miller began the 2023 season back with Arkansas, struggling to an 0–2 record and 6.41 ERA in 4 starts in April.
On May 1, the Mariners announced that Miller would be promoted to the major leagues for the first time to start against the Oakland Athletics.
[11] In his first start, he took a perfect game into the sixth inning before giving up a one-out single to Tony Kemp.
In his first three starts, Miller allowed only eight baserunners, breaking the MLB record held since 1901, with a minimum 15 innings pitched.