Career
Football Club In the spring 2015, Mathisen has frequently trained with the F.C. first team and played several matches for the reserve team He was in the squad for the 2015 Danish Cup Final, but remained on the bench for the whole match. Three days later Mathisen got his first team debut, when he substituted Daniel Amartey in a 2-0 loss against Football Club Midtjylland.
Mathisen was permanently promoted to the first team squad on July 13, 2015.