The tri-captain of the '70-71 team, Bill Mainor became just the 12th person in Fordham history to score 1,000 points. During the 1970-71 season, he set the second-best mark at the time for free throw percentage (.809) in a season, and finished his career with a .780 free throw mark. Mainor had his best season as a member of the varsity in 1970-71 when he averaged 14.1 ppg, including a 27 point effort in a win over Notre Dame at sold-out Madison Square Garden. He set his career high with a 32-point performance in the Rams' loss to Louisville in the 1970 NIT.

After graduation, he was drafted in the sixth-round by the New York Knicks in 1971.