Ghana midfield star Kevin-Prince Boateng is set to miss this month's World Cup playoff against Egypt after picking up an old injury with his club Schalke. Boateng picked up a knee injury during Schalke's Bundesliga win over Augsburg one day ago and was rated doubtful for the Egypt game, having already had six operations on the same place. With 10 days to go until the match, Schalke sports director Horst Heldt implied that the former AC Milan midfielder ‘would have to cancel his invitation for the Ghana national team'. Meanwhile, Boateng admitted that he is struggling with the nagging injury but indicated that he will wait for further results. "I got a blow out, it is swollen, we must wait and see," the 26-year-old was quoted by Ghanasoccernet.com. "I had some pain and was hoping it will go away. Knees – that's always been my problem area." Should Boateng be confirmed out against Egypt, Ghana manager Kwesi Appiah will be left in a further unenviable position after losing key defense trio John Boye, Jonathan Mensah and Isaac Vorsah in addition to midfielder Mohamed Rabiu.