Borussia Dortmund chief Hans-Joachim Watzke says Nuri Sahin has been proved wrong over his move to Real Madrid.
Sahin has struggled since joining Real from Dortmund last summer.
"Nuri's transfer to Real was a mistake," Watzke told Bild. "It would have been better for him if he had stayed with us."
"But Nuri is a fighter. A return is currently not an issue."