Potvin began his professional hockey career in December 1969 with the Springfield Kings in the American Hockey League (AHL). The next season in 1970–71, he led all defencemen on the team in scoring as he played on the Springfield Kings' Calder Cup-winning team with teammates Butch Goring and Billy Smith. During that playoff season, Potvin scored two goals and 10 assists for 12 points in 12 games. Ten years later, Goring, Smith, and Potvin would play together again on the first two New York Islanders' Stanley Cup-winning teams, in 1980 and 1981.