The Chelsea midfielder suffered the injury at the end of Friday's training session and was sent to hospital where a scan revealed the full extent of the problem.
The 29-year-old is certain to miss Sunday's Premier League trip to Aston Villa and a major question mark hangs over whether he will be fit for England's crucial Euro 2008 double-header.
McClaren's men are up against Israel at Wembley on 8th September before taking on Russia four days later.
So far there hasn't been any splash moves in the transfer market with only spare parts and youngsters getting moved today -- to stay up with the latest, click here.
