Borussia Dortmund chief Hans-Joachim Watzke admits they could be forced to sell Ilkay Gundogan.
Gundogan has baulked at agreeing new terms with BVB amid strong interest from Manchester United and Real Madrid.
"Of course, we try to always keep our top players, it's quite normal and we want to extend Ilkay's contract. But we must also see a sale as a possibility," said Watzke
"In 2011 we lost Nuri Sahin (Real Madrid), who was named player of the year in the Bundesliga, and we survived. Hopefully we can do it so that only a top player leaves this year, namely Robert Lewandowski.