A 2011 graduate of Catholic High School (LA), Aaron was voted “Mr. Baseball” for the state of Louisiana during his senior season. He attended Louisiana State University and was honored as the 2014 National Pitcher of the Year by the College Baseball Foundation. In 2014, Aaron was a Golden Spikes Award finalist, named First-Team All-American, SEC Pitcher of the Year and First-Team All-SEC.
Aaron was the first player drafted by the Phillies to make his major-league debut the very next season since Pat Combs in 1989. He was the seventh overall selection in the 2015 amateur draft.