[bbfan1991]

Manchester United boss Sir Alex Ferguson could be without Wayne Rooney, Phil Jones, Rio Ferdinand and Nani for Saturday's FA Cup fourth-round tie at Anfield.

Rooney, Jones and Nani picked up ankle knocks during Sunday's Premier League victory away to Arsenal, while Ferdinand expected to play in that match but was ruled out with a recurrence of a back problem.

Reports on Friday suggest that Rooney has been unable to take part in training all week - although his problem is not expected to rule him out of action in the long-term.

United have struggled with injuries all season: Ashley Young and Tom Cleverley are both thought to be at least a week away from returning, Anderson is sidelined for a fortnight and Darren Fletcher and Nemanja Vidic are out for the season.

Meanwhile, Ferguson called on both sets of fans to keep a lid on their tempers ahead of the potentially explosive clash at Anfield. "It's a massive game for both clubs," he said. "There's a tremendous profile around it. Steven Gerrard said it's the responsibility of the players to behave properly and I expect my players to. And also the fans. Both sets of fans need to make sure we're talking about the game and nothing else."