In 1968 Jack Rathwell began his professional hockey career with the Clinton Comets, of the Eatern Hockey League. Captain Jack Kane led the Comets, so to avoid confusion his fellow players started calling him "Jake". The Comets had just won the Walker Cup in the previous season. In the right winger's rookie season, Rathwell helped the team win a second successive Cup. To top off his stay in Clinton, the next season Jack Flirted with the 100 plateau and lead the team during the playoffs to another Walker Cup victory, the team's third straight title.
Jack also began a five year connection to Joe Robertson while in Clinton. From 1968 to 1973 they kept winding up in the same cities. In the 1970 off-season the pair were picked up by the WHL Salt Lake Golden Eagles. Owner Dan Meyer was looking to bolster his lineup by buying players. Rathwell responded by capturing the 1970-71 WHL Rookie of the Year honors. Jack's coach, Gus Bodnar, called him "a great National Hockey League prospect" he's dedicated, wants to play in the NHL and some day he will.
1971-72 saw Rathwell move to the California Golden Seal organization and then on to the Buffalo Sabres farm team. With Cincinnati, along with Robertson, they contributed to another playoff championship by capturing the 1973 Calder Cup. Two more trades put Jack Rathwell in the Boston Bruins system, where he played for the Rochester Americans in the AHL. In 1974 the Don Cherry coached Bruins put in the call to Rochester for an emergency call-up. Jack Rathwell was the player selected to join Boston.
On January 27, 1975, Jack Rathwell became an official NHL player. The game was memorable for the fact that it had three Temiscamingue natives in the team lineups. Rathwell joined Andre Savard and Richard Lemieux as representatives of the small Quebec town. Jack Rathwell chose to retire at the end of the season to devote time to his growing family. He decided that his newborn daughter should not be put through the constant shifts that a minor league player endures. Jack kept active in local games and by coaching minor hockey.