Manchester United manager Alex Ferguson has a worry hanging over his head ahead of the Manchester Derby this weekend. That worry is United's leaky defence, so far this season it has conceded 32 goals and that is far below an acceptable standard for the Old Trafford outfit. There was hope that Nemanja Vidic may have returned to the squad for the big game, but he is not going to be ready after being ruled out of the Champions League game at home to CFR Cluj on Wednesday night. Fergie reflected back to the game against Reading when asked about the defence by reporters, he said: "It is a worry. If we perform like that on Sunday then God knows what’s going to happen to us. Saturday was like Cartoon Cavalcade and when you see City have Balotelli, Dzeko – really tall players – it’s going to be a big challenge. It’s a concern. "But that’s on Sunday. It’s five days away, and at this moment in time it feels like five months."