Sebastien Haller resigned from Dortmund training just a few weeks since arriving from Ajax owing to a medical problem. Sebastien is wished a swift recovery and a quick return to the pitch by the entire Borussia Dortmund family, and Dortmund will do everything in its power to make sure he receives the greatest care.
it has been confirmed by Dortmund and the club's medical team sentenced Haller to have a testicular tumor and must undergo treatment first for now and must stop all activities including pre-season.
It's a shame because it would be great if Haller could follow suit, but health is paramount and his focus must be there first so he can recover quickly and rejoin Dortmund as a ready player.