Ghana midfielder Kevin-Prince Boateng has suffered a knee injury which could spark worries for Black Stars coach Kwesi Appiah ahead of next month's crucial World Cup playoff against Egypt.

The versatile player, who plays for German top-flight club Schalke, has been ruled out of Wednesday's German Cup game against Darmstadt because of the setback.

The injury is similar to what he suffered before Ghana played against Zambia in a World Cup qualifier this month, ruling him out of the match in Kumasi. Boateng missed training with Schalke on Tuesday before coach Jens Keller confirmed that the Ghanaian has been unable to train because of injury. The extent of the fresh knee injury is unknown but what is clear is that he is unable to play for the side when they take on Darmstadt.

“Draxler and Boateng will not be included in the squad due to injuries," Keller told reporters.

The injury will be a worry for Ghana coach Kwesi Appiah who is preparing to name his squad for next month's playoff against Egypt.

Appiah will be hoping that Boateng will make a full return to fitness before the Black Stars squad is named for the anticipated difficult match in Kumasi on 15 October.

Ghana will need all of its best players to be available for the match to ensure that the Black Stars get a handsome victory in the first-leg before the return leg is played away from home.

The match will decide which country qualifies for the 2014 World Cup in Brazil.