The reality is that the lad doesn't seem capable of settling anywhere. Left Watford for us, left us for Dortmund, now leaving Dortmund for the rags. Arguably some bad behavior in there too. I don't want him to go to the rags because I don't want to have to deal with them claiming they're the big boys pinching our players, but I'm not honestly worried about him being there long term.
Couple of years down the line he'll be trying to go to Madrid or Barca if he improves and if he doesn't he'll be doing a Lingard/Young/Lukaku and trying to go to Inter.