Marsh was born and grew up in Milwaukee, Wisconsin and attended Ronald Wilson Reagan College Preparatory High School.

[4] Marsh was selected in the Competitive Balance section of second round of the 2019 Major League Baseball draft by the Kansas City Royals.

[5] He signed with the team he was assigned to the Idaho Falls Chukars of the Pioneer League, where he started 13 games and posted a 4.05 ERA in 33+1⁄3 innings pitched.

[13] In 14 starts split between Northwest Arkansas and the Triple–A Omaha Storm Chasers, Marsh registered a cumulative 5–3 record and 4.62 ERA with 75 strikeouts in 62+1⁄3 innings pitched.

[17] While playing the Toronto Blue Jays on April 24, Marsh took a line drive to the forearm off the bat of Addison Barger.