Newcastle United boss Kevin Keegan sees Sunderland rival Roy Keane as a potential Manchester United manager.
"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."