Manchester United boss Sir Alex Ferguson admits a 4-3 win at Reading isn't ideal preparation for next week's derby.

Ferguson has a defensive headache going into the clash with Manchester City.

"It is a massive game, if we defend like that we will be in trouble, there is no doubt about that.

"I think the important thing for us is to take lessons from the mistakes we are making and find a solution, because we are going to need it."