Gelsenkirchen - FC Schalke 04 captain faces several weeks on the sidelines after tearing an adductor muscle in Tuesday's 3-1 defeat to Real Madrid CF in the last-16 of the UEFA Champions League.
The 26-year-old had to be helped off the pitch at the Santiago Bernabeu, with an MRI scan later confirming the unwanted news.
"It's tough," lamented head coach Jens Keller. "Personnel-wise we're down to the bare bones. We'll have to find a solution."
Jefferson Farfan (knee), Christian Fuchs (knee surgery), Felipe Santana, Atsuto Uchida (both muscular) and Christian Clemens (pubic bone) have already been ruled out of Saturday's clash against Eintracht Braunschwig, while long-term absentees Dennis Aogo, Marco Höger and Jan Kirchhoff have only recently returned to light training.