Following a promising rookie campaign on the blueline, posting 21 points in 62 games with the Generals, in the 2015–16 season, Stillman was selected in the 2016 NHL Entry Draft by the Florida Panthers, 114th overall.
During his final junior season in 2017–18, Stillman was traded by the Generals to contending club, the Hamilton Bulldogs in exchange for future draft picks on December 28, 2017.[3]
On March 5, 2018, Stillman was signed to a three-year, entry-level contract with the Florida Panthers.[4] He established new career highs with a combined 29 assists and 34 points, in helping the Bulldogs claim the J. Ross Robertson Cup.
Professional
After attending the Panthers 2018 training camp, Stillman was assigned to begin his professional career with AHL affiliate, the Springfield Thunderbirds, for the 2018–19 season.[5] Exhibiting a responsible two-way game with the Thunderbirds, Stillman posted 11 points through 46 games before he received his first recall to the Panthers on February 26, 2019.[6]
He made his debut that night for the Panthers in a 4–3 overtime defeat to the Arizona Coyotes at Gila River Arena in Glendale, Arizona.[7] In playing for the Panthers, Stillman joined his father in becoming the first father and son to have played with the franchise.[8]
On April 25, 2021, Stillman signed a three-year, $4.05 million contract extension with the Blackhawks.[10]
Approaching the 2022–23 season, Stillman was traded by the Blackhawks to the Vancouver Canucks in exchange for Jason Dickinson and a second-round pick in the 2024 NHL Entry Draft on October 7, 2022.[11] Stillman limited through injury, appeared in 32 games with the Canucks and registered 5 assists. Nearing the NHL trade deadline, the Canucks dealt Stillman to the Buffalo Sabres in exchange for prospect Josh Bloom on February 27, 2023.[12]
After parts of two seasons within the Sabres organization, Stillman left the club as a free agent and was signed to a one-year, two-way contract with the Carolina Hurricanes on July 3, 2024.[13]