David Moyes's biggest difficulty at the start of his reign as manager of Manchester United may simply be that he is not Sir Alex Ferguson.
Although the first years of Ferguson's reign were notoriously difficult, since that first title in 1993 there has been a sense of solidity and stability about Old Trafford: even when the squad occasionally looked weaker than that of some of their rivals, you knew that because of Ferguson they would challenge, that there would be no capitulation. United's form was a given: that sense of assurance isn't there any more.
That isn't to say that Moyes is a bad manager. On the contrary, his record with Everton has been excellent: on extremely limited resources he has kept them in the top half of the Premier League on a consistent basis and, while there has been some sniping that he never led them even to a league Cup, he did get to the FA Cup final in 2009.
Realistically, with a club of Everton's resources, he has done an exemplary job. If he played negative football at times, well, he was manager of Everton: what was he supposed to do? The question, though, is: how useful is that as preparation for managing Manchester United.
A former director of a Premier League club, lamenting a bad appointment his club had made, once said to me that you should never put somebody who's only run a corner shop in charge of a multi-national. Up to a point, of course, the analogy is a good one.
There is a real skill in running a club on a shoestring, hunting down bargains and free transfers, promoting youth, finding a tactical system for players who are not necessarily especially gifted and motivating them. There is also a skill in handling the egos of superstars, in finding a way for them to play, of existing as a cog within a much larger corporate machine. Those skills are related, but they are not the same. Moyes has not been existing at corner-shop level, but equally Manchester United is a huge step up. His Champions League experience amounts to one qualifying-round tie, against Villarreal in 2005, that was lost.
A club of United's stature has a problem when appointing a new coach simply because there are so few comparable clubs. Do they appoint a proven winner with Champions League experience who has no first-hand knowledge of English football? Or do they do what they did, which was to take somebody with impeccable Premier League credentials but no experience at the very highest level? There is no right answer and either option is a gamble.
That so many clubs go down the foreign route, which is a major problem for British managers: they compete their badges and perhaps get a job in League Two. They do well and are given a chance in the Championship. They win promotion but then spend a season scrapping against relegation with a squad that isn't really good enough for the Premier League and find themselves written off as bottom-end fighters.
Aidy Boothroyd, now manager of Northampton in League Two, is a classic example, scorned as a long-ball coach because of the way his Watford side played on their way to relegation - which seemed to ignore the fact that a) it was Watford, and pretty rubbish Watford at that and b) he had got them promoted in the first place. A manager can only work with the resources he has.
At United, Moyes will have the very best resources. There are questions to be answered about the future of Wayne Rooney and perhaps the need for a more dynamic midfielder to win the ball before Michael Carrick distributes it, but Ferguson has left behind a hugely gifted young squad that should go on to win vast amounts of silverware. The assumption is that had Ferguson stayed on, they would have done, and that is another problem for Moyes.
He has no credit in the bank. Ferguson could lose a few games - not that it happened very often - and nobody would be overly concerned; the assumption, based on years of experience, would be that he would turn it around. Moyes has none of that, and United do have a tricky start. They begin at Swansea City, where they only drew last season, and are then at home to Chelsea and away to Liverpool. It's perfectly conceivable that, without even playing that badly, they could fail to win any of those games and then suddenly Moyes would be under pressure, his every move scrutinised, and each subsequent game would become even harder. That then would be a test of Ferguson and whether he really is able to walk away or whether he will start interfering.
United have suffered the problem before, when Wilf McGuiness and Frank O'Farrell found themselves haunted by Matt Busby's shadow round every corner. Bob Paisley had to ban Bill Shankly from the Liverpool training ground so his authority would not be undermined. Even if Ferguson is careful, it will not be easy for Moyes to impose himself.
The question will always be asked: what would Ferguson have done?
And that uncertainty means that United's form is less easy to predict than at any other time in the past two decades. With new managers at both City and Chelsea, this could be the most open Premier League for years.