Kevin Keegan has backed Roy Keane to step into the Manchester United hot-seat when Sir Alex Ferguson eventually calls time on his career.

The Newcastle boss goes head-to-head with his Sunderland counterpart in Sunday's Tyne-Wear derby showdown at St James' Park fully expecting Keane to one day be managing the Old Trafford giants.

Keegan said: "Will he be manager of Manchester United one day? You would not bet against it, would you?

"There's Roy and Mark Hughes at the moment and then there is still Sir Alex, who will still be there for another 30, 40 years.

"Roy is getting a grey beard now, he might have a longer one by the time he gets it.

"I said to Alan Shearer the job will come for him at Newcastle United - and it will come for Roy Keane at Manchester United after Sir Alex."

Former England boss Keegan is relishing the derby meeting with their bitter local rivals, and is looking forward to more Premier League meetings between the two in years to come.

He added: "Roy has proved to be a very, very successful manager at Sunderland in getting them up and to stabilise them in this division.

"I know some of our fans say they'd like to see them go down, but these games are very special.

"This is our biggest game of the year."