Switzerland coach Ottmar Hitzfeld is anxiously awaiting news from his medical staff on the condition of Alexander Frei after the captain limped out of the team's final training session in Zurich on Wednesday.
The striker remained on the ground after a tackle from Steve von Bergen and, after receiving treatment from the team doctor and physio, he was helped away from the field and may not be able to board the flight which takes Switzerland to South Africa on Wednesday night.
"I hope he has not torn any ligaments or fractured anything," said Ottmar Hitzfeld. "We have sent Alex to hospital to get a clear diagnosis."
He added: "At the moment, I presume that he will be able to fly with us. You have always got to think positively. Although he had a lot of pain, we have got to hope that he can play in the tournament, even if he cannot play in the opening game."