Manchester United have confirmed that versatile defender Phil Jones has been ruled out for two months after undergoing knee surgery.
Jones, who has yet to make an appearance for United this season after picking up a back complaint in preseason, sustained the injury during training and is now set to be sidelined until early November.
A statement on the United website said: "Phil Jones has had surgery on a knee meniscus tear sustained in training that will require six to eight weeks of rehabilitation."
The 20-year-old's extended absence leaves manager Sir Alex Ferguson short of defensive options, with midfielder Michael Carrick being deployed at centre-back earlier in the season.
England international Jones joins defender Chris Smalling on the sidelines, who is suffering from a broken metatarsal.
Until either player returns, Ferguson will have to rely on the trio of Nemanja Vidic, Rio Ferdinand and Jonny Evans as his three senior centre-back options.
The surgery means Jones will miss a succession of key league fixtures, including matches against Liverpool, Chelsea and Arsenal. In addition, he will miss at least the Red Devils' opening three Champions League group matches.
Even when he has recovered, Jones' lack of match fitness may prove a significant problem in regaining the form which at one stage saw him compared to Duncan Edwards during an exceptionally encouraging debut campaign following his big-money move from Blackburn in 2011.