Playing his first professional season with the Eastern Hockey League's Philadelphia Ramblers, Rupp was loaned to the Detroit Red Wings on the night of March 22, 1964 when Wings starting netminder Terry Sawchuk came down with a sudden injury. Rushed in just in time for the game, Rupp played admirably in a 4-1 loss against the Toronto Maple Leafs.
Earlier that same season Rupp, who was born in Detroit, tended the crease for the American Olympic team at Innsbruck, Austria games.. He went 2-3 with a GAA of 4.00. He would also participate for Team USA at the 1968 games in Grenoble. The Americans did not medal in either Olympics, finishing in 5th and 6th place respectively.
Rupp finished the season with the Ramblers, and then moved to the EHL's New Jersey Devils for the 1964-65 season. Half way through that season he ended up with the IHL's Dayton Gems. Rupp would stay in the Ohio city for the next 6 seasons.
Rupp retired in 1972 but resurfaced in the lowly NAHL 3 years later. He was filling for the Buffalo Norsemen who had injury problems.
Rupp passed away from cancer in 2006. Living in Dayton, Ohio at the time, Rupp was 63 years old. He had enjoyed a second career as a financial planner, owning his own business with his wife, Kathy.