The Denmark international moves to the Bundesliga side on a four-year deal after making just six starts in the Premier LeagueViktor Fischer has left Middlesbrough after just one season to join Bundesliga side Mainz on a four-year deal.
The Denmark international moved to the Riverside from Ajax, where he forged a reputation as an exciting winger and won two Eredivisie titles during four seasons in the Dutch capital.
However, Fischer endured a disappointing spell in England and racked up just six Premier League starts as the club were relegated straight back to the Championship.
Fischer has consequently opted for a new direction in his career and links up with Mainz, who finished 15th in the Bundesliga last term, until 2021.
"Mainz is the right club for me to be able to really enjoy my football again," he told the club's official website.
"They have a great stadium, I want to be a part of this team and this club quickly, find my form and show my qualities as an attacking player. "
While Fischer has signed on at Mainz, Jhon Cordoba has left the club to join Bundesliga rivals Cologne on a deal until 2021.