[3][4] He signed and made his professional debut that year with the Rookie-league Arizona League Indians where he was 1-1 with a 4.87 ERA in 20+1⁄3 relief innings pitched.

Milbrath spent the 2016 season with the Lynchburg Hillcats of the High–A Carolina League where he pitched to a 3-5 record with a 5.43 ERA in 41 relief appearances.

He began the 2017 season with Lynchburg, where he was taught to pitch sidearm, before receiving a midseason promotion to Akron.

[9][10] He competed for a spot on Pittsburgh's 2018 Opening Day 25-man roster,[11] but was waived and returned to Cleveland before the start of the regular season.

[17] He appeared in 6 games for the Double-A Wichita Wind Surge, but struggled to a 10.00 ERA with 12 strikeouts in 9.0 innings pitched.