Johannesburg: England captain Rio Ferdinand was taken to hospital after suffering a left knee injury in the final minutes of their first training session on Thursday.
The injury-prone 31-year-old central defender went into a tackle and fell badly, said manager Fabio Capello who announced the setback for his squad at his first news conference following the opening session at the England training camp.
He had just confirmed that goalkeeper David James had missed training due to a nagging knee injury aggravated by the long overnight flight from London on Wednesday.
He said: "More bad news -- Rio (Ferdinand) suffered a knee problem and he has just gone to hospital for a scan. We hope it is not a bad injury but that is all we know."
He also confirmed that midfielder Gareth Barry was recovering well after injury. He said Barry, who had injured his right ankle, trained well and was "improving every day".
The England manager added that he was thrilled to be in South Africa and was revelling in finally having a serious game to prepare for. "It is seven months now since our last qualifying game," he added.
England play their first game against the U.S. on June 12.
Ferdinand took over as England captain after fellow defender John Terry was stripped of the job in February because of an off-pitch scandal involving his private life but he has not played regularly for Manchester United this season due to a succession of injuries.
He played for England in the 2002 and 2006 World Cup finals tournaments and has made a total of 78 appearances, scoring three goals.