The 21-year-old was taken by the Florida Panthers with the 114th overall pick in the 4th round of the 2016 NHL Entry Level Draft. After numerous years of development in the OHL, Riley Stillman would further his development in the AHL with the Springfield Thunderbirds during the 2018-19 pro-hockey campaign.
The native of Canada experienced a relatively decent first season in the AHL. While lacing up in 59 AHL regular-season games, Stillman would go on to record 4 goals and 13 assists for 17 points, along with 52 penalty minutes and a +8 rating.