Borussia Dortmund chief Hans-Joachim Watzke admits Mats Hummels could be sold this summer.

The Germany defender has been linked with a move to Manchester United.

"In this moment this is a dummy situation because there is no offer. If one arrives, we will discuss it internally and make a decision," Watzke said.

"We've lost one major player each year but we don't stop playing football.

"Mats knows his contractual situation. The decision where he will play next season will be taken by BVB."