Sullivan was a A two-sport captain his senior year (football and baseball). He scored his first Holy Cross touchdown in the Crusaders' historic 55-12 over Boston College in 1942. He left for the service for four years, but came back and was a unanimous choice for the O’Melia Award as the outstanding player in the 1947 BC game. He was All-East and All-New England choice as a senior and also won the coveted Bulger Lowe Award as New England’s most outstanding football player in 1947. He was the third-ever Crusader to win the award. He played in the East-West Shrine game and College All Star game after his senior season, and played one season of pro ball with the San Francisco 49ers before settling in for a career in teaching.