Born in Canada but also holding an El Salvador citizenship, Matthaus was part of the Toronto FC Academy, for which he played between 2021 and 2022. He then moved to Cambridge United, playing for their U21 team.
In January 2023, he signed a professional contract with El Salvador first division club A.D. Chalatenango. Matthaus appeared in 9 matches in the top flight in El Salvador, before returning to Canada and signing for BVB IA Waterloo in League1 Ontario last summer.