Schalke 04 head coach Jens Keller has revealed that he is unsure how long he will be without Kevin-Prince Boateng.

Boateng has an ongoing knee issue, which Keller said will be scanned in the coming days, but the coach hopes that the midfielder will be fit to play after the international break.

"The knee is still swollen and an examination of the extent of the injury will follow," Bundesliga.com quotes Keller as saying. "The most important thing is that he's back on the pitch next week."

Boateng joined Schalke from AC Milan in the summer transfer window.