Johnson spent one season as Houston's OC/QBs coach. He spent the three previous seasons as Mississippi State's quarterbacks coach under Mullen, where he helped develop the 2016 NFL Rookie of the Year Dak Prescott.
Before his time at Mississippi State, Johnson became the youngest offensive coordinator in the Football Bowl Subdivision when he got the Utah job at age 24.
Johnson is the fourth assistant Mullen has hired who previously work with him at Mississippi State, joining Billy Gonzales, John Hevesy and Todd Grantham.