Manchester United manager Sir Alex Ferguson has admitted that he was "surprised" when defender Rio Ferdinand was selected in Roy Hodgson's England squad.

The 34-year-old, who has not donned an England shirt since June 2011, was named in the squad to face San Marino and Montenegro in the Three Lions' World Cup qualifiers this month.

Despite Hodgson's decision, Ferguson has claimed that it is not a certainty that the centre-back will join up with his national teammates.

"I was as surprised as anyone when I heard," Ferguson said in a press conference. "I need to speak to the [United] doctor because we prepare Rio Ferdinand in a certain way and there are certain treatments he has to go through.

"He has to make sure he is going to be OK in terms of the number of games he plays. We have been doing that for two years and it has worked. We have to look at all these things before Rio decides [if he joins up]."

United are preparing to take on Reading in the Premier League tomorrow.