Karlsruhe have announced the transfers of Matthias Zimmermann and Lukas Rupp to Borussia Monchengladbach.
The young duo have signed for the Bundesliga side for an undisclosed fee, with German reports suggesting it to be in the region of €2.5 million.
Zimmermann, captain of Germany's Under-19 squad, has made several appearances for his country at youth level and is highly regarded in his homeland.
Karlsruhe sporting director Oliver Kreuzer admitted it was a considerable loss to lose such players, but underlined they did not want to stand in the way of the duo making it to the first divison.
"We had constructive talks and were able to find a solution that we can live very well with," Kreuzer told Karlsruhe's official website.
"Of course we wanted to continue with the two players for the new season, but we can also understand their desire to take the next step and play in the highest league in the Germany."