Schalke general manager Horst Heldt has hit out at Japan coach Alberto Zaccheroni after defender Atsuto Uchida's thigh strain in the friendly against Latvia added to the Bundesliga club's injury problems.
Heldt, whose club are tenth in the Bundesliga, said: "It angers me, when we urged Uchida not to travel to Japan for a midweek friendly against Latvia.
"But the Japan boss insisted on his inclusion and Uchida returned with an injury. It makes me sick."
Schalke boss Jens Keller, now without a string of key players, said it almost seemed as though the club was "under a curse".
Keller is without Klaas-Jan Huntelaar, Lars Unnerstall, Ibrahim Afellay, Kyriakos Papadopoulos, Ciprian Marica, Christoph Moritz and Uchida through a variety of injuries, while Peru international Jefferson Farfan (viral infection) and Marco Hoger (cold) are doubts for the game against Mainz at the weekend.
"We're really suffering at the moment, but complaining won't get us anywhere," Keller said. "We have to come to terms with the situation and make the best of it. The players who are fit are working really well in training."
Keller could make tactical changes for the Mainz game, with reports suggesting that Germany international Julian Draxler could be used as a "false nine".