Borussia Dortmund have told Chelsea and other clubs to forget about bidding for Nevan Subotic.
The Serbian international is widely regarded as one of the best young defenders in Europe.
Chelsea are understood to be looking to bolster their defence during this window and were linked with a near £20million bid for the 22-year-old.
However, Dortmind chief Hans-Joachim Watzke insists that none of the clubs top talent will be sold - even if they received a 'fantastic' offer.
"We will not sell any player this winter, full stop," Watzke told Nachrichten.
"We do not even think about selling anyone during the summer. Should there be a fantastic offer dropping in for any player and given this offer would be also of significance for Borussia Dortmund, we would still remain very much unprepared to sell.
"Of course, in a given case we would consider it. Anyway, we are not allowing any young player to leave us."