Manchester United boss Sir Alex Ferguson says Rio Ferdinand's injury suffered in victory over Fulham is not serious.

Ferguson explained that Ferdinand's injury should not prove too serious, after he was substituted despite the match being precariously balanced towards the end.

"Rio got a bit of stiffness," said Sir Alex. "He gets that, you know, from time to time, the stiffness in his back. So we brought on Chris Smalling as a safeguard.

"If Rio had played it out, he would probably have managed it okay but then not be available for a couple of weeks so I think we've done the right thing at the right time."