Duncan played college football at Tennessee from 1979 to 1983. Along with teammates Willie Gault, Anthony Hancock, Lenny Taylor and Tim McGee, he helped create the school's reputation as "Wide Receiver U." He played sparingly in 1979, redshirted in 1980, played as a defensive back in 1981, and played primarily as a reserve receiver in 1982. In 1983, however, he led the team in receiving with 33 catches for 640 yards and six touchdowns. He caught touchdown passes of 80 yards and 57 yards in Tennessee's 41-34 win over Alabama, and his 85-yard touchdown catch against Vanderbilt remains the third-longest in school history. He attracted close attention from scouts for his workout performance at the 1983 Blue–Gray Football Classic.