First, I felt it would be disrespectful to talk of replacements. Then I realized, that's not the nature of the club, like Sir Alex would say. The nature of the club is to go on, to move and get stronger. So while there can't be any replacements for that huge, Fergie sized hole in the club, there can be a successor.
So, who would it be?
Jose Mourinho is the most obvious choice for many. He is fighting to quit Real Madrid, where his position has well and truly become untenable. He has also shown an admirable maturity in a number of his dealings with the club - definitely more than at Chelsea, Inter or Porto before that. Let's put it this way - the Mourinho of ten years ago could not have dealt with the Madrid media this way. This has been the biggest issue United's board have supposedly had against him - that and his tendency to buy big.
David Moyes is a candidate who's leaped to the front of the pack over the last year. Scottish, severe and motivated, he carries more than a passing resemblance to the Knight of Old Trafford. His lack of big-budget experience and Europe, though, are major drawbacks in the eyes of many. Moyes is one of the gentlemen in the game, and believes in doing things the right way. There are theories that he can succeed at a big club, but without proof they are just theories. Will the board take the risk? The bookies think so - they slashed odds on Moyes the beginning of the week, much before any sound of retirement came out of Old Trafford. Clearly, they knew something we didn't.
The Fergie Alumini have been touted more than once. Ole Gunnar, Ryan Giggs, and the like. However, they would represent significant risks as none of them have both the required experience (in Ole or Ryan's cases), nor the success (Steve Bruce, Mark Hughes and Bryan Robson etc), to warrant a call up.
Manuel Pellegrini, Jupp Heynckes and Jurgen Klopp have all been mentioned over the last week in the media. How reliable these reports are, well, nobody really knows.
What do you think - who will take up the most attractive, yet impossible task of Manchester United in the post-Ferguson era?