He then served as the defensive coordinator for Division-II member Lock Haven University for three years (1987–1989), before becoming the school's head coach in 1990.
In 1996, Therrell joined Todd Berry's coaching staff at Illinois State University as the defensive coordinator.
Following the 1999 campaign, Therrell followed Berry to the United States Military Academy, where he served as the defensive coordinator for four seasons (2000–2003).
[1][2] After coaching three seasons in the professional ranks with the Las Vegas Locomotives of the United Football League (UFL), Therrell returned to Murray State as defensive coordinator in 2013.
[3][4] Therrell served as head coach at his alma mater, Bledsoe County High School, during the fall of 2017, leading the Warriors to a 4–7 record.