(CNN) -- Manchester United will be without central defender Rio Ferdinand for up to a month, the English Premier League champions said on Friday.
Ferdinand is struggling to recover from a thigh injury he picked up in training.
Ferdinand sustained a minor muscle tear in his thigh in training last week ahead of United's opening league match of the season against Birmingham and the injury has not improved.
United manager Alex Ferguson told his club's official Web site that he would be sidelined for "hopefully three, but maybe four weeks."
The English champions clearly missed Ferdinand and his central defensive partner Nemanja Vidic for the opening victory over Birmingham and the shock 1-0 defeat to Burnley in midweek.
Ferdinand is also set to miss the next two England games, a friendly against Slovenia on September 5 and a key World Cup qualifier against Croatia four days later.
Ferguson is hopeful that Vidic will be fit to return for United's match against Wigan on Saturday.
"We don't have any new injuries from Wednesday night. They're all fit," he told www.manutd.com.
"The one position we're hoping for an improvement in is with Vidic. He's trained now for 10 days and he is ready for a game. Hopefully he'll be OK for Saturday."
Ferdinand also has the experience of former England international Gary Neville to turn to as they bid to bounce back after the Burnley defeat. "Gary Neville played 15 minutes at Burnley and he could be ready too, and that gives us experience at an important time after defeat on Wednesday," added Ferguson.
Ferdinand had endured a frustrating spell with injuries, missing key games in United's title run-in last season due to back and rib injuries, returning for the Champions League final defeat to Barcelona.