Mostardi's best season as Kent State's quarterback was a junior in 1958, when he led the Golden Flashes to a 7-2 record, completing 30-of-66 passes for 542 yards and six touchdowns and rushing for 302 yards. He was named first-team All Mid-American Conference in '58 and was a second-team all-conference pick as a senior. He also was named team captain and most valuable player in 1959. After graduation, Mostardi played briefly with the Cleveland Browns and the Minnesota Vikings in the NFL and with the Oakland Raiders of the old American Football League. The epitome of a student-athlete, Mostardi earned a doctorate in physiology at Ohio State in 1968. He was elected to the Kent State Sports Hall of Fame in 1988.