England manager Fabio Capello has placed Michael Dawson on standby after captain Rio Ferdinand was seen leaving hospital on crutches after picking up a training ground injury on Friday.
The England players had been taking part in their first training session since arriving in South Africa when the Manchester United star sustained a knee injury at their Rustenburg training base.
Ferdinand has endured an injury-plagued campaign with United, largely because of a troublesome back problem.
However, there was some good news for Capello as Gareth Barry was able to return to training, having been sidelined with an ankle injury since 5 May.
Capello said: "Barry has started training with the team today and he is improving every day. He is getting better and better and will train again this afternoon. We know we have to be careful with him.
"Other bad news is that Rio hurt his knee in the last moment of training in a tackle. He has gone to the hospital for a scan and we hope he will be ok.
"We hope it will not be so bad but we have Michael Dawson on call."