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. 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. Prior to graduating, Rathbone was drafted 95th overall in the 2017 NHL Entry Draft by the Vancouver Canucks.