Manchester United's pre-season hasn't exactly gone to plan.

With a number of players yet to return from their World Cup break, no wins on their tour and Jose Mourinho being his petulant worst, there are very few positive noises coming from the club this summer.

Their three signings of Lee Grant, Diogo Dalot and Fred haven't inspired a huge deal of confidence, particularly when rivals Liverpool have been splashing the cash to add real quality to their squad.

Mourinho has been railing against chief Ed Woodward, saying in a recent press conference that he hopes just one of the five signings he wanted at the start of the window will arrive at Old Trafford before the end of the window.

However, time is ticking for the Man United boss and there's a real chance that he might miss out on all of his transfer targets and the Red Devils will have to do make do with their current lot.

Here are the potential consequences of the Red Devils failing to add to their squad before the window slams shut at 17:00 on 9 August.

Same old defensive frailties

Phil Jones and Chris Smalling in action for Manchester United against Chelsea in the FA Cup final

Manchester United only conceded one more goal than Manchester City in the Premier League last season which would imply they had a strong defence.

However, David de Gea was forced into action 115 times over the course of the season, the fifth most of any goalkeeper in the league, whereas Ederson only made 58 saves.

This shows the disparity between the two clubs, with United relying on de Gea's brilliance rather than breaking down attacks beforehand.

Dalot will help provide assurance at wing-back but centre-back is the real problem area for Mourinho and if he doesn't get it sorted, Chris Smalling, Eric Bailly, Marcos Rojo and Phil Jones will continue to rotate depending on who's fit at that moment.

Pogba becomes disillusioned

Paul Pogba comes on from the bench

Paul Pogba's turbulent relationship with Mourinho has been well-documented, with the Portuguese boss dropping him midway through last season.

The powerful central midfielder showed the world what he has to offer at the World Cup, leading his country to victory and showing his ability when not bound by Mourinho's stifling style of play.

When Pogba signed for what was then a record fee, he would have been given assurances that United would be winning trophies and continuing to make marquee signings but that hasn't really happened.

If Mourinho fails to add to the squad, his relationship with Pogba could worsen and there will be no shortage of options for the Frenchman if he wants to force a move later down the line.

Youngsters get their chance

Mourinho is not known for giving youth a chance with Marcus Rashford and Anthony Martial frozen out last season following the arrival of Alexis Sanchez, but he may not have many other options this season.

He has been complaining about having to play a young team on tour in the USA, but some have shown that they could make the grade in the first team come United's league curtain raiser at Leicester City.

Andreas Pereira has shone in pre-season and has been one of the few highlights of a dismal tour.

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The 22-year-old has looked very sharp, scoring United's only goal against Liverpool and his performances have led fans to clamour for more regular appearances for the midfielder.

Timothy Fosu-Mensah could also profit from the lack of competition by staking a claim for a first-team spot in defence.

The 20-year-old spent last season on loan at Crystal Palace and will now have decent top flight experience and represents a solid option for Mourinho, particularly if the defence suffer their habitual injury problems.

Mourinho gets the sack

Manchester United manager Jose Mourinho looks dejected after defeat

Could it be a case of third-season syndrome again for Jose Mourinho?

He's been making the same grumbles he made before his final catastrophic year at Chelsea regarding the lack of signings and the poor preparation for the season.

If the board aren't backing him in the transfer market, perhaps it's because the Special One has an expiry date and they're not confident in his ability to manage the club.

If no more signings come through the Old Trafford gates, expect there to be fireworks and many people wouldn't be wholly surprised if there's a different face in the dugout come the end of the season.