The key Man Utd figures which highlight the huge challenge facing Ole Gunnar Solskjaer

Ole Gunnar Solskjaer's first full season in charge of Manchester United kicks off against a backdrop of growing unrest among supporters, who are accusing the club of empty promises, lack of ambition or even ability to lead them back to the summit of the game.

Football is played on the pitch, rather than a spreadsheet, but for disgruntled fans the numbers simply don't add up - be it in terms of net spend or debt levels at Old Trafford.

Another summer of recrimination and fury directed at owners, the Glazers, and executive vice-chairman Ed Woodward has placed yet more pressure on Solskjaer to get the campaign off to a flying start before frustrations erupt.

So how has it come to this?

Crunch the numbers and the challenge facing Solskjaer becomes clear.

£66m net spend

In Pictures | Man Utd's summer transfer business

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…and falling. The deadline day £73.7m sale of Romelu Lukaku to Inter Milan served to hugely offset a spending spree of £140m on Harry Maguire, Aaron Wan-Bissaka and Daniel James.

That figure is likely to be further reduced by the potential departures of Marcos Rojo and Matteo Darmian before the transfer windows around Europe close next month. And if Marouane Fellaini's move to Shandong Luneng in January – at a cost of around £7m – is also factored in, United's total expenditure for the calendar year could fall to well below £50m.

Hardly the sort of overhaul supporters expected after last season's sixth-place finish and failure to qualify for the Champions League.

Solskjaer insists he had more money to spend – but was intent on bringing in the 'right targets.' Yet those words sound hollow to the club's following, who have seen a succession of windows slam shut, with crucial business still to be concluded.

32 points to make up on Man City

In Pictures | Manchester City fans celebrate title win | 15/04/2018

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The gulf between the Manchester rivals is enormous and in danger of widening.

Solskjaer claimed before the end of last season that it would take a miraculous campaign to mount a serious title challenge – and the fear is United have fallen further behind Pep Guardiola's domestic treble-winners.

Compared to United's net spend of £66m, City's is £93m for the summer, with Guardiola breaking the club's transfer record to sign midfielder Rodri and making Joao Cancelo the most expensive full-back in Premier League history.

City may have lost the leadership qualities of Vincent Kompany, while Leroy Sane will miss the majority of the season after suffering knee ligament damage – but there is every reason to believe the best are only about to get better.

Five missed targets

In Pictures | Every Man Utd signing since Sir Alex Ferguson left

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Solskjaer needed a perfect summer, but ended up falling well short of the required business to turn the club around.

Late moves for Paulo Dybala, Christian Eriksen and Mario Mandzukic were evidence of a transfer strategy that became more scattergun as the window progressed, with United desperately trying to address key issues in midfield and attack.

Jadon Sancho was always the top attacking target – but that move never got off the ground.

Sean Longstaff would have added numbers in midfield and was seen as another who fit the drive to recruit emerging domestic talent, but United dropped interest in the face of Newcastle's £50m valuation.

Two summers in which Pogba has agitated to leave

In Pictures | Man Utd's 10 most expensive signings

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Perhaps Solskjaer's biggest challenge is trying to get the best out of a player, who made it abundantly clear he doesn't want to be at the club.

Paul Pogba's future has cast a shadow over United's summer, ever since he declared his desire to seek a 'new challenge.'

In other words, a move to Real Madrid.

United's valuation of £150m-plus was successful in frightening off the Spanish giants – but the impact on Pogba's state of mind remains to be seen.

The World Cup winner is vital to Solskjaer's plans, playing in a two, alongside Scott McTominay, in a 4-2-3-1 formation.

It has looked promising in pre-season – and may just mean United see the best of their £89m record signing.

The hope is Pogba will be re-energised within a young and exciting team, rather than being demotivated by his failure to force a move.

Two protest campaigns

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The #GlazersOut and #WoodwardOut movements have gathered pace the longer the summer has gone on.

There have been no shortage of conspiracy theories either regarding the pacing of United's business, in what some fans claim was a strategic move to distract the most disgruntled sections of support.

Woodward was subject to a plane protest at the start of last season – but the appointment of Solskjaer and a heady three months after his arrival, eased unrest.

A miserable end to the campaign and an underwhelming transfer window has seen attentions turn to the running of the club once more.

Should the season get off to a slow start, the ire of fans will be aimed directly at Woodward and his American bosses.

One striker who has scored 20 or more goals in a Premier League campaign

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United must replace Lukaku's goals – and the pressure is on Marcus Rashford and Anthony Martial to prove they can be prolific at the highest level.

For all the criticism Lukaku was subjected to, no United forward scored more than him in his two years at the club.

Alexis Sanchez is the only player left at Old Trafford who has managed 20 or more league goals in a season – yet the Chile international has scored only three in 32 Premier League appearances for United.

Rashford has made a point of distancing himself from the role of No9 this summer, with Martial – who scored 17 in his first season in English football - expected to lead the line.

The France international is considered the best finisher at the club – and Solskjaer is hoping he can be the manager who finally untaps his considerable potential.

Handing him the No9 shirt, which Jose Mourinho stripped him of, was an astute touch.

Seven (7!) centre backs

In Pictures | Harry Maguire joins Man Utd | 05/08/2019

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It says everything about United's issues in defence that Solskjaer made Maguire his priority signing this summer, despite inheriting six central defenders.

His failure to offload any of them during this window is symbolic of a lack of ruthlessness, which he promised at the end of last season.

Fans have been quick to remind Solskjaer of his claims that certain players would be cast aside following an end to the campaign that saw United win just one of their last nine games in all competitions.

Of the starting XI that suffered a humiliating 4-0 defeat at Everton in April, only Lukaku has gone.

Elsewhere, Antonio Valencia left as a free agent – as did Ander Herrera, although United desperately tried to keep hold of the Spaniard by offering him a contract worth more than £200,000-a-week.

It's not just the lack of incomings that has so infuriated supporters – but the failure to trim such a bloated squad.

New contracts for Chris Smalling and Phil Jones were met with widespread ridicule, while Matteo Darmian remains at the club, despite being a virtual spectator for the past two seasons.

24 – The average age of the likely starting XI against Chelsea

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Sir Alex Ferguson famously proved you can win with kids – and Solskjaer's drive to fill his squad with young and enthusiastic players is commendable after the staid performances of recent years.

United's energy levels are expected to increase significantly this season, with the Norwegian implementing a front-foot style of pressing football, more akin to that produced by City, Liverpool and Tottenham in recent years.

Mason Greenwood, at 17, will be given the chance to establish himself in the first team – and the hope is that he can become the surprise package of the season.

Three trophies in six seasons

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United's wilderness years have still provided a reasonable return of trophies – the FA Cup, League Cup and Europa League.

That haul pales in comparison to the glory years under Ferguson, but still makes them one of the most successful clubs in the country over that period.

Fans want more – but they also want the football to go with it.

Solskjaer accepts the title is beyond his side – but a piece of silverware, along with real signs of progression on the pitch, will go a long way to appeasing the crowd and buying himself more time to complete his overhaul.

His biggest issue is the Europa League, Thursday night football and all of that.

It is the competition that may well provide him with the best chance of securing a return to the Champions League. Yet given the taxing nature of the Europa League, he might be better advised to concentrate on domestic matters and use it as an opportunity to give fringe players game time.

Eight months since re-starting technical director recruitment process

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It was around this time last year and the fall-out of Mourinho's final transfer window that Woodward decided a director of football was the way to go.

Mourinho's reluctance to work within such a structure meant it wasn't until the former manager was sacked in December that United seriously reignited their pursuit.

By March the role had been changed to technical director – and the right cultural fit was the overwhelming quality they were looking for.

Mike Phelan, Rio Ferdinand and Darren Fletcher have all come under consideration – but some eight months on, no candidate has been appointed.

The lack of a figure between the board and manager to oversee the transfer policy has hardly helped during such a pivotal window.

It is now vital an appointment is made in time to ensure next summer is more successful.

One vision?

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For all of the complaints from supporters, the signs are that United are heading in a new direction.

Solskjaer has implemented a clear philosophy – and the signings of three Englishmen point to a focused strategy.

A move for Sancho could well be reignited at the end of the season, when West Ham's Declan Rice could also be on the agenda.

A 4-2-3-1 system has given United a distinctive shape that has been lacking for some time, and the attacking, pressing game witnessed in pre-season is true to the club's traditions.

Inside the club, the insistence is that Solskjaer will be given more windows to complete his overhaul and he is seen as the long-term solution.

Given the challenges he faces ahead of this campaign, that stance may well be tested to the limit over the next nine months.