[3] Schwellenbach was selected in the 34th round of the 2018 Major League Baseball Draft by the Cleveland Indians, but opted not to sign with the team.
[6] Following the season he played collegiate summer baseball for the Traverse City Pit Spitters of the Northwoods League, where he hit for a .356 average over 22 games.
[14] He was named the winner of the John Olerud Award as the nation's best two-way player after finishing the season with a .284 batting average and a .403 on-base percentage with six home runs and 40 RBIs while also posting a 3–1 record with ten saves and a 0.57 ERA over 18 pitching appearances.
[18] Shortly after signing, Schwellenbach underwent Tommy John surgery to repair the Ulnar collateral ligament in his pitching elbow.
[22] Schwellenbach split the beginning of the 2024 season with the High–A Rome Emperors and Double–A Mississippi Braves, accumulating a 1.80 ERA with 51 strikeouts across 8 starts.