With early years spent with the Ohio AAA Blue Jackets, he played junior ice hockey for the Oshawa Generals, winning the Memorial Cup with the team in 2015.

Upon his release from Belleville, Cassels resumed his North American career, agreeing to a contract with the Utah Grizzlies of the ECHL on October 2, 2019.

[8] On July 30, 2021, Cassels extended his career in the AHL, agreeing to a one-year contract with the Cleveland Monsters, affiliate to the Columbus Blue Jackets.

[9] As a free agent from the Monsters organization, Cassels left for Europe for the second time in his career, agreeing to a one-year contract with Swedish club, Södertälje SK of the HockeyAllsvenskan on July 26, 2022.

[10] Cassels registered just 2 assists through 13 games to start the 2022–23 season with Södertälje SK, before opting to leave Sweden and return to the AHL in signing a one-year contract for a second stint with the Belleville Senators on November 2, 2022.