Schalke striker Jefferson Farfan will be out of action for at least four weeks with a shoulder injury.
The recent €10 million (£7.9million) signing from PSV Eindhoven fell awkwardly following a foul during the Royal Blues' 1-0 UEFA Champions League victory over Atletico Madrid on Wednesday.
An MRI scan on the 23-year-old's shoulder on Thursday revealed significant ligament damage which will keep the Peru international out of action until at least mid-September.
The news is a massive blow to ambitious Schalke, who face Hannover, Werder Bremen, Bochum and local rivals Borussia Dortmund in the coming month, as well as the Champions League return leg in Madrid.
"The news is a bitter blow for both the lad and for the whole team," Schalke team manager Andreas Muller told Bild.