In 1986, Darnell joined the staff of Al Groh at Wake Forest University as assistant head coach and defensive coordinator. He spent two years with the Demon Deacons before accepting the same position at the University of Florida in 1988. In each of his two seasons at Florida, his defenses ranked third nationally and first in the Southeastern Conference. In the middle of the 1989 season, he took over for his fired predecessor, Galen Hall, as head coach at Florida, leading the Gators to a 3–4 record over the season's final seven games.