He was the team's linebackers coach, a job he got in part due to his relationship with John Harbaugh. During his time at WMU, Mattison coached alongside John Harbaugh, who was a graduate assistant and assistant coach.
Mattison held the position of linebackers coach for the team, which was secured in part through his relationship with John Harbaugh. While at Western Michigan University, Mattison worked alongside Harbaugh, who served as a graduate assistant and assistant coach.