Ex-Manchester United boss Sir Alex Ferguson has praised Dwight Yorke for his immediate impact at Old Trafford following his transfer from Aston Villa.

Ferguson was talking about the time it takes for a new signing to adapt to life at United, and referred to Yorke as an exception.

The former striker, who signed from Villa for £12.6 million in 1998, was instrumental for the Red Devils in winning the treble in his debut season with the club.

Ferguson told ESPN: "[Louis Van Gaal has] certainly made a lot of changes and he's bought [six] new players this year and, I think, five or six new players the year before.

"That takes time and it's not easy. Coming to Manchester United, you do need time. In my time, there was maybe Dwight Yorke who gave an immediate response - he was fantastic from day one.

"They are not always like that. He was an exception. It normally takes some time, particularly if they come from abroad, to settle in."