MIDDLESBROUGH, England, Sept 2 (Reuters) - England head coach Steve McClaren believes Rio Ferdinand can be one of the best defenders in the world and has asked the Manchester United player to 'prove his credentials'.
Speaking ahead of England's vital Euro 2008 qualifiers against Israel and Russia later this month, McClaren told reporters: 'Rio has the potential to be one of the best centre-halves in the world and I've always believed that.
'But he needs to step forward and deliver that. Rio is a very important part of our team, not just defending but coming out with the ball and expressing himself. That's something I think he can do more of.
'Sometimes he's like the swan, serene on top but paddling away underneath.'
Ferdinand, 28, has played 60 times for his country, scoring once, and his £29.1 million move from Leeds United to Manchester United in 2002 is still the record fee ever paid for an English player.
McClaren has injury worries for the two qualifiers at Wembley Stadium against Israel on Sept.8 and Russia on Sept. 12, games England must win to keep alive any realistic hope of qualifying for next year's finals in Austria and Switzerland.
They are currently fourth in the group three points behind the joint leaders Croatia and Israel, but the injuries could harm their cause.
The latest concerns Chelsea midfielder Frank Lampard, who has a torn his left thight muscle while David Beckham and Kieron Dyer are also out injured along with Gary Neville and Ledley King.
Lampard has been the target of what McClaren feels is unfair criticism from a section of England fans.
'I think it's undeserved and I don't think his performances have warranted that,' he said.
'I have always stressed that our fans are the best in the world. But the best reaction from Frank was his performance against Germany and I thought he was excellent in that game. He has to keep performing like that.
'We had a good chat before the Germany game and I was delighted with his reaction because he got a fair bit of criticism after the Israel and Andorra games, and his reaction has been first class.
'We're delighted with his performances. We could have done with a few more goals -- but then he got one against Germany, and he's been scoring for Chelsea.'
Lampard, however, could well be missing from both qualifiers and, with fellow midfielder Steven Gerrard nursing a hairline fracture in a toe and not yet certain to play, McClaren will be looking for all his fit men to do their bit in securing two wins.