Duncan played his first collegiate football season for the Duke Blue Devils under Wallace Wade in 1946.
Duncan then spent three seasons as a standout defensive lineman for Peahead Walker's Wake Forest Demon Deacons.
Duncan was a linebacker and defensive end for the New York Giants of the National Football League (NFL) from 1950 to 1955.
[3] In 1965, Duncan joined the Saskatchewan Roughriders of the Canadian Football League (CFL) as an assistant under head coach Eagle Keys.
Duncan became head coach of the Calgary Stampeders in 1969, replacing Jerry Williams who left the team to join the Philadelphia Eagles.