[3] Growing up in Massachusetts, Rathbone played ice hockey for the Mass Midget Select League's Cape Cod Whalers and Dexter Southfield School.
[5] Although Rathbone missed four weeks of the season due to a concussion, he was still considered a ALL-USA Player of the Year candidate.
[10] Rathbone joined the Harvard Crimson men's ice hockey team to compete in their 2018–19 season[11] and received the Don Parsons Memorial Scholarship in recognition of his "character, community service, leadership and academics.
[15] Rathbone re-joined the Harvard Crimson for his sophomore year and recorded 31 points in 28 games as the season was cut short due to COVID-19.
[19] On October 17, 2023, Rathbone was traded by the Canucks alongside Karel Plášek to the Pittsburgh Penguins, in exchange for Mark Friedman and Ty Glover.