Manchester United boss Sir Alex Ferguson is full of praise for Aston Villa counterpart Martin O'Neill.

O'Neill has been mentioned as Ferguson's successor at Old Trafford and the Scot said: "Martin is unquestionably one of the best managers in the game. He has proved himself.

"The only way you can be classed as a great manager is by proving yourself over a period.

"Martin has done that - look at his time at Leicester and Celtic and the job he is now doing at Villa.

"He is obviously a top manager. There's no question about that."