Ryan Giggs is not up to the task - Manchester United are broken so badly they need a big personality to carry out the overhaul

The size of the rebuild needed at Old Trafford is a task way beyond Manchester United's most decorated player

Contrary to appearances, there can be harmony when Louis van Gaal and Roy Keane stand together. It was at Lansdowne Road in 2001 that the Dutchman acknowledged the Irishman's man-of-the-match display in the 1-0 victory for his country which ended the Netherlands' hopes of qualifying for the 2002 World Cup. Keane subsequently secured one vote for the World Player of the Year award – from Van Gaal.

Beyond that, the prospect of the two working in tandem at Old Trafford – a notion which grew legs after it was floated in Wednesday's Irish Examiner – does have potential to be hugely divisive. There are already doubts in the Netherlands about how Van Gaal would co-exist with Sir Alex Ferguson, having been in a state of civil war with the Bayern Munich president Uli Hoeness when he left his last club management job there in 2011.

Keane has certainly put differences behind him in the past, working for the Football Association of Ireland in the past five months despite a decade lambasting the national set-up, on and off, but it will be a brave man who puts those two in charge of United together. Keane's relationship with Ferguson seems unsalvageable, given that the older man appears even less forgiving.

But while the combustible, uncompromising nature of Van Gaal calls into question the value of such a personality being front-runner to succeed David Moyes, the state United are in suggests that they will need an individual of such character.

Liverpool's managing director Ian Ayre was reflecting earlier this week on how much more difficult it had been to buy elite players while out of the Champions League. You can't trade on your name, he said. "That's the reality. There is definitely a challenge." And some who were present at Manchester City in the summer of 2010 after they had only qualified for the Europa League can tell United that players will take some persuading.

City wanted to buy the Spanish midfielder Xabi Alonso from Liverpool that summer, discovered he just was not interested and instead found themselves shopping for Gareth Barry, who they managed to get into a taxi from Dubai – where he was holidaying – to Abu Dhabi's Emirates Palace hotel, while Liverpool manager Rafael Benitez – who also wanted Barry – wasn't looking.

United believe that the name of their great club will insulate them from shopping in downmarket stores – yet salvaging something from the wreckage of the Moyes era will entail living with the consequences of the steps taken to help him succeed. There is a view inside football that the £300,000-a-week salary United agreed to keep Wayne Rooney away from Chelsea was ludicrous: a millstone around the club's neck and something agents will use as a benchmark when United come knocking. "The agent will want 300, so the club will say 200 and they'll end up agreeing on 250," one insider observed.

Also, if the big-name players are on £250,000, the lesser ones will want £80,000. That is how it starts to play out when agents know, as they will with United, that they are dealing with a club newly eliminated from the Champions League and so desperate to make it back at the first attempt. Meanwhile, clubs will use Juan Mata's £38m transfer fee as a benchmark. United can only go for a certain marque of player, too. Things will not come cheap. United's situation resembles the one City found themselves at, five years ago.

It takes a manager capable of dropping his trousers and revealing what lies beneath – as Van Gaal once did – to hold on to a sense of value in the face of such factors. The managers just desperate to survive will not care what the cost might be to United or to chief executive, Ed Woodward, an excellent businessman and negotiator but one still finding his way in football.

United are engaged in another pressurised search to restructure the team, top to bottom, because the legacy handed on by Ferguson simply was not good. The player-recruitment systems were little less than shambolic. There was none of the five-year advance planning, with due diligence done on emerging talents from all corners of the world, which you will now find at the touch of a button at Chelsea and City – prime practitioners of the acquisition business who analyse the market to death.

The manager who took over from Ferguson was always going to struggle with that side of the inheritance. Moyes found himself handed what became known as "the black box" – a loose, unfathomable system of agreements and communications between Ferguson and his scouts. United began equipping Moyes with modernity but they have only just begun.

The size of overhaul needs a magisterial grip from someone with a big, macro picture of running a club. It is a task way beyond Ryan Giggs – despite the sense from the top of United that the chance to be manager has come just a few years too soon for him.

Van Gaal proved in the way he brought through a new generation of players at Bayern Munich five years ago that he does have that experience and capability. Sparks will fly if he becomes United's manager. There may be minimal harmony. But a big personality looks necessary to get United out of this pit and on to an upward trajectory.