The Manchester United star left hospital on crutches after undergoing a scan on the knee injury suffered during the final minutes of England's second training session at their Bafokeng Sports Centre base.

The problem resulted from Ferdinand being on the receiving end of what coach Fabio Capello described as a "minor tackle".

But the fact that Michael Dawson was immediately put on stand-by by the Italian suggested the setback is more than a minor scare, and now Sky Sports News claim Ferdinand is out.

Ferdinand had been talking optimistically only 48 hours ago about leading England to World Cup glory.

He insisted anything less than winning the competition would not be regarded as a success and that England were "not here to make up the numbers".

But his own days as part of the 23-man squad now appear numbered, shattering his hopes of playing in a third World Cup after being an unused member of the 1998 squad.

Capello has stressed his confidence in England being able to make a strong challenge if they have all their key players available and Ferdinand falls into that category.

He confirmed: "In the last moment of the training, Rio suffered a problem with the knee.

"He has gone to hospital for a scan. We hope it will not be so bad an injury but we have Michael Dawson on call.

"It came from a minor tackle during the training. It happened in a normal tackle.

"It is his left knee. How bad is it? We will have to wait and see."

The Ferdinand-John Terry partnership has been earmarked to play a key part in England's bid for glory this summer, despite injuries restricting the number of times they have appeared together.

Ferdinand had an injury-hit season at Old Trafford, being laid low for considerable periods with back and groin problems.

But he was happy with his fitness at the end of the season and during England's two-week training camp in Austria before coming through the friendly internationals with Mexico and Japan unscathed.

Capello's alternatives in the current squad are West Ham's Matthew Upson and Tottenham's Ledley King.

Upson has started nine of the last 17 internationals while King has forced his way into Capello's thinking despite his long-term knee setback.

King has impressed for Tottenham this season although by his own admission he looked far from convincing in the recent friendly with Mexico at Wembley.

Dawson was named in Capello's initial party of 30 for the finals but was excluded from the final 23 after not playing against either Mexico at Wembley or Japan in Graz.

He has had an outstanding season at Tottenham, often alongside King.