After bringing 10 Premier League titles and two European Cups to Old Trafford during an incredible 22-year reign, the Manchester United boss has earned the right to end his tenure at a time of his choosing.

But he realises many of his management rivals are not so lucky and said: "It is a very precarious industry."

Roy Keane has just quit as Sunderland boss, while another of Ferguson's former players, Paul Ince, is now under severe pressure at Blackburn.

And with Howard Wilkinson, Alan Curbishley and Sam Allardyce, the favourite to replace Keane, currently out of work, Ferguson accepts job security is virtually non-existent.

"Very few managers last more than three or four years with a club nowadays and the lifespan of a manager is getting shorter and shorter," he added.

"I count myself fortunate to spend so long at one club.

"I have not had to go through that turmoil. It is horrible."