DeMarco played his first two professional seasons in the CHL minor league, earning brief NHL callups to New York. In 1971–72, he played with the Rangers full-time, appearing in two thirds of the scheduled games, recording 4 goals and 11 points in 48 games. Late in the 1972–73 season, DeMarco was dealt to the St. Louis Blues. Given an opportunity to play more and receive time on the power play, DeMarco responded with 13 points in 14 games, to give him a total of 30 points on the season.
