St Pauli Hamburg are losing midfielder Marcel Hartel who played a key role in their promotion back into the Bundesliga after 13 years.
The club said that Hartel, who scored 17 goals and had 13 assists as St Pauli finished top of the second division, will not renew has contract beyond the season.
"It is not easy for me to take this step. But sometimes life offers special opportunities," Hartel said in a statement.
Leaving after three years without naming a future club, Hartel added: "I am proud of what we have achieved here. I will never forget that."
Sporting director Andreas Bornemann said: "We would have liked to have kept Marcel for a longer period but we respect his decision."