Growing up in Massachusetts, Rathbone played ice hockey for the Mass Midget Select League's Cape Cod Whalers and Dexter Southfield School.[2] During his first year with the U18 Whalers team, he recorded eight goals and 18 points which he superseded the following year by posting 16 goals and 35 points in 22 games.[5] Although Rathbone missed four weeks of the season due to a concussion, he was still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.[6] Rathbone committed to play NCAA Division I ice hockey with the Harvard Crimson in 2015[5] but chose to complete his education at Dexter rather than join the United States Hockey League (USHL) to remain closer to his family and autistic brother.[7]
Throughout the 2016–17 season, Rathbone split his time between the Whalers, Dexter, and Youngstown Phantoms in the USHL. He played four games with the Phantoms and recorded one assist.[8] During his senior year at Dexter, Rathbone was named captain and was ranked 57th overall by the NHL Central Scouting Bureau in their final ranking of North American skaters.[9] Prior to graduating, Rathbone was drafted 95th overall in the 2017 NHL entry draft by the Vancouver Canucks.[10]
Collegiate
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."[12] As a freshman at Harvard, Rathbone skated in 33 games and finished the season with seven goals and 15 assists for 22 points. His first collegiate goal came against the Quinnipiac Bobcats on November 2, 2018, and he finished the year with a seven-game point-streak.[13] His seventh point in the same number of games came during a loss against Clarkson which effectively knocked Harvard out of the ECAC playoffs.[14] As he completed the season second amongst league rookies in points, he was named to the ECAC Hockey All-Rookie Team.[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.[13] Prior to the seasons' cancellation, Rathbone earned national recognition with an election to the First Team All-ECAC Hockey team[16] and AHCA All-American First Team.[17] Once the season was cancelled, Rathbone returned home and debated whether he should return to college or start his professional career.[3]
Professional
On July 14, 2020, Rathbone signed a three-year entry-level contract with the Canucks, thus concluding his collegiate career.[18] On May 6, 2021, Rathbone scored his first NHL goal in a 6–3 win against the Edmonton Oilers.[19]
As a free agent from the Penguins, Rathbone was signed to a one-year, two-way contract with the Buffalo Sabres on July 1, 2024.[21]
International play
Rathbone was named to Team USA to compete during the 2015 Under-17 Five Nations Tournament.[22] He recorded two goals in their final game against Germany to clinch first place at the tournament.[23]
^Raptis, Mike (March 16, 2019). "Rathbone Builds On Breakout Season". Vancouver, British Columbia, Canada: The Province. Retrieved January 10, 2021 – via newspapers.com.