The Lombard, Illinois product attended Glenbard East High School, where he earned all-state honors as a senior, while leading team to a conference championship. As a junior Sebby turned in a 1.98 ERA, while hitting .308 with 14 extra-base hits. During his senior year he posted an 11-0 record, 0.78 ERA and 95 strikeouts while hitting .431 with 8 home runs and 33 RBI. He earned all-conference and all-area honors his final two seasons, as well as being named the team’s MVP both years. The lefthander attends Illinois State University, where as a freshman in 2017 he made 14 appearances out of the Redbirds’ bullpen. He put up a 5.06 ERA with a strikeout rate just shy of 24% and a .282 batting average against. In 2018 Sebby posted a 3-1 record in 19 appearances out of the pen, recording a dominant 26.5% strikeout rate in 21.2 innings.