The Swiss international has impressed since signing for the German side in January.
He has now caught AC Milan’s eye and they could test Borussia’s desire to keep the midfielder.
The start of the 2017-18 Premier League season is just around the corner and is shaping up to be one of the most competitive yet.
As always it is the so called “big clubs” that have splashed the most cash in the transfer window so far this summer. Manchester United or City? Arsenal or Tottenham? Who are the winners and losers of the transfer window so far?