At 19, Cyr earned a spot on the Sabres' roster despite having a year of junior eligibility remaining. He played in 36 games with Buffalo, scoring 15 goals and 27 points. He also played 20 games with the junior Cougars and was on a goal-a-game scoring pace, with 21 goals and 43 points in just 20 games.

In 1983-84, Cyr joined the Sabres full-time, playing in 71 games and scoring 43 points. The following year, he scored 46 points on 22 goals and 24 assists. He upped his total to 51 points in 1985-86, his most productive offensive season in the NHL. That is where Cyr's career peaked. After playing in 71 games for three consecutive years, he played in 73 games in 1986-87, but his offensive production drastically declined to just 27 points. In 1987-88, he had just a single goal and an assist after the first 20 games of the year. By now, the Sabres' brass had lost confidence in Cyr, and he was traded to the New York Rangers. In 40 games with the Rangers, he managed just four goals and 17 points.

In 1990-91, Cyr joined the Hartford Whalers, playing in 70 games, but the offensive prowess was nowhere to be found. He scored 12 goals and 25 points. He returned for one last go-round with the Whalers in 1991-92, but after 17 games, he failed to record a goal while notching three assists.

Cyr retired from professional hockey following the 1992-93 campaign in which he played with the Springfield Indians of the AHL. One of his biggest thrills as a hockey player was winning a gold medal with the 1982 Canadian team at the World Junior Hockey Championships in Minnesota. Cyr was one of the team leaders, scoring four goals and ten points in seven games. The 7-0 victory over the former Soviet Union is a game which no doubt stands out in the minds of all the players from that team.