The Scotsman contemplated retirement a few years ago but signed a fresh deal at Old Trafford instead but at 62, Ferguson may decide to retire at any point.

"We keep our eye on managers but it is difficult - whoever today’s hot star is might be cold tomorrow," Gill told the club's website.

He added: "We just monitor it and make sure we are aware of developments in European football management.

"It’s not like a normal business where you can groom a number two internally because it is not always feasible.

"And, quite rightly, there are rules about targeting managers who are doing jobs with other clubs.

"But as and when Sir Alex decides to retire, I am sure there will be no shortage of applicants."   

Ferguson received the knighthood a few years back after guiding Manchester United to a terrific Champions League, FA Cup and Premier League title in one season. He has made The Red Devils into one of the biggest clubs in the world and is an Old Trafford legend.