Career
Duhnke played youth football for FV Karlstadt and 1. Marius was promoted to the reserve team two years later, although Manuel had since moved on, and made his debut on the opening day of the 2012-2013 season, as a substitute for Fabian Hürzeler in a 1–1 draw with Football Club Augsburg II in the Regionalliga Bayern. He ended the season as Bayern Munich II"s top scorer, with fifteen goals, fourteen of which had come in the second half of the season, as the team finished in second place.
Despite this, though, Duhnke left Bayern in July 2013, believing he had little chance of breaking into the first team, and signed for SpVgg Unterhaching of the 3.
Liga. He made his debut for the club on the opening day of the 2012-2013 season (his 20th birthday) as a substitute for Janik Haberer in a 0–0 draw with Jahn Regensburg.
