"The three teams at the top are looking very strong and nobody is making mistakes. It means the results against each other could be vital. Chelsea certainly are going to be a challenge and on Sunday there will be so many good players on the pitch it can't fail to be a good game."
Ferguson is confident his captain Roy Keane will make it after missing the midweek trip to Panathinaikos with a hamstring injury. "It was a slight strain rather than anything serious," said the United manager.
Ferguson also had praise for Chelsea's unsung hero Claude Makelele, who helped Real Madrid beat United in the Champions League last season.
Ferguson said "I am not surprised Madrid wanted to keep him - he is a formidable player."