In 2019, Selby spent the season with Single–A Greensboro Grasshoppers, pitching in 17 games and registering a 6–3 record and 2.97 ERA with 86 strikeouts in 88.0 innings of work.

[3] He returned to High–A Greensboro in 2021, making 31 appearances out of the bullpen and logging a 4.37 ERA with 67 strikeouts and 6 saves across 59+2⁄3 innings of work.

[7] He spent most of the season as the Indians primary closer, posting a 3.86 ERA with 6 saves in 28 appearances prior to his promotion.

[8] On August 8, 2023, Selby was promoted to the major leagues for the first time, making his debut the following day against the Atlanta Braves.

[16] On July 11, 2024, the Royals traded Selby to the Baltimore Orioles in exchange for cash considerations.