Manchester United manager Sir Alex Ferguson has revealed defender Rio Ferdinand is likely to be out for at least two weeks with a thigh injury.The Scot was speaking after his side's 1-0 Premier League victory over Birmingham, which Ferdinand missed.
"I would imagine Rio will be out for two weeks," said Ferguson.
Ferdinand, 30, will undergo a scan on Monday and could be a doubt for England's World Cup qualifier with Croatia on 9 September at Wembley.
In Ferdinand's absence, John O'Shea captained United as they began the defence of their Premier League title with a slender home win over Birmingham City, courtesy of a Wayne Rooney
Ferdinand had shaken off the back injury he picked up during England's midweek 2-2 friendly draw with Holland, but is now likely to miss United's Premier League fixtures at Burnley and Wigan and the home match with Arsenal.
United are already without Ferdinand's regular central defensive partner Nemanja Vidic for two weeks with a calf injury and full-backs Gary Neville (groin) and Rafael (shoulder) are also short of fitness.
Jonny Evans began the game against Birmingham but was withdrawn after 75 minutes as a precaution following a recent ankle injury.
United had defenders Wes Brown and Ritchie De Laet on the bench for the match, in which United were far from their best but claimed the three points courtesy of Rooney's side-foot finish after his initial header had struck the post.
"We had some good opportunities and played some good football and in general I am satisfied with the result," Ferguson told Sky Sports.
In the dying moments, substitute Michael Owen could have doubled United's advantage with a goal on his Old Trafford debut when Rooney played him clean through, but Birmingham's on-loan keeper Joe Hart saved his effort.
Ferguson backed his summer signing, saying: "Owen made a great run and the keeper made a great save. But he will get his goals, no question about that.
"There are plenty of games coming up in the next few weeks to give him his opportunity and he will take them."
Birmingham had their chances to take something from the game and their manager Alex McLeish was pleased with his side's performance.
"It is the most we have created here, certainly from my experiences here," he said. "I was disappointed we didn't quite nail one of the chances.
"We worked hard and the organisation of the team was great and they applied themselves brilliantly within the system.
"They showed they are a team that never gives up."