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 today.
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 tonight.
"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.
"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."
Should the 30-year-old be ruled out of the World Cup, it would be yet another severe blow both for the player and the national team.
Frei tore knee ligaments during the first half of Switzerland's first game of Euro 2008 against the Czech Republic and had to leave the field in tears and follow the rest of the competition from the sidelines.
He is Switzerland's all-time top goalscorer with 40 goals and has just returned to his best form with 15 goals for Swiss champions FC Basle in 19 games last season.
For such a player, Hitzfeld says there is no replacement.
"Maybe I have somebody right in the back of my mind, but we have got to think positively," he said. "I hope that he is fit again soon, and I believe he will be."
Hitzfeld also refused to blame Von Bergen for being over-zealous in his tackle, saying it is important that the team is treating training seriously.
"We are preparing for a World Cup and you have got to have tackles," he said.
"The players have got to train hard, at a high pace and of course you risk injuries.
"We are preparing for the games against Spain, Chile and Honduras and we need a certain level of intensity."
With or without Frei, Hitzfeld is confident his side can come through their group, although he is refusing to think of anything beyond the first stage just yet.
"I also dream that we go a long way, but they are dreams," said the two-times Champions League winning coach.
"The reality is that a great result would be getting into second round, and when you are there, the dream is the quarter-final and so on."
Realistically, though, even Hitzfeld knows European champions Spain are going to be a cut above.
"Chile will be our biggest rival for second place," he said.