Manchester United have been one of the Premier League's busiest clubs in the transfer market this summer, signing five players at a cost of just over £76million whilst rightfully parting with the likes of Tom Cleverley, Nani and Robin van Persie.

Yet the Red Devils are still very much a work in progress and especially in regards to claiming next season's title - which would be their first since Sir Alex Ferguson's retirement two years ago - there's plenty of areas within the squad that require further improvement. Another dose of fat trimming certainly wouldn't go amiss either.

So with that in mind - and to give Louis van Gaal some guidance on what his next move in the market should be - we've listed FIVE burning 'transfer issues' the Old Trafford outfit are yet to resolve.

Which of these FIVE do you think van Gaal should be addressing first Man United fans? Let us know by commenting below!

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WHICH CB SHOULD LVG TURN TO NEXT?

Ramos2

Louis van Gaal has made his preferred template of centre-half abundantly clear; a top class defender with leadership skills, an array of international and European experience and perhaps most importantly of all, quality and confidence on the ball.

Mats Hummels and Sergio Ramos both firmly fall into that category, as World Cup-winning centre-backs famed for their ability to bring the ball out of defence, but both have snubbed the chance to move to Old Trafford this summer. The former rejected a United switch back in May, whilst reports this morning claim the latter is now set to sign a new contract - outrageous pay rise included - at the Bernabeu. Likewise, Manchester Evening News claim van Gaal has never been interested in mooted back-up target Nicolas Otamendi.

So who could the Red Devils feasibly turn to next? In terms of ball-playing defenders, Tottenham's Jan Vertonghen and Everton's John Stones particularly come to mind. But neither are what you'd define as 'top class' defenders and both would require substantial transfer fees to convince their respective clubs to sell to a Premier League rival.

Meanwhile, Zenit's Ezequiel Garay has been on the United radar ever since the Sir Alex Ferguson days, whilst Schalke's Benedikt Howedes and Juventus' Leonardo Bonucci, who have all featured in either World Cup or Champions League finals over the last year, often feature in the tabloids' rumour columns too.

But the latter duo have both rejected the chance to leave their current clubs already this summer - Howedes deciding not to take advantage of his £12million release clause and Bonucci signing a contract extension until 2020 earlier today - and you get the feeling LVG would have snapped up the easily obtainable Garay already if his interest in the Argentina international was genuine.

Suddenly Manchester United are running out of options. But by hook or by crook, they need to find a solution by the end of the summer window.

SEND THE YOUNGSTERS OUT ON LOAN

Nick Powell

Traditionally, Manchester United have always been luxury to rather enormous squads, predominantly propped up by the sizable amount of young talent bursting through from their academy ranks.

But few would dispute that loan moves are an important stage of development for most young players and despite having a wealth of youthful prodigies on the books, only a handful have secured a temporary switches so far this summer - striker Will Keane joins Preston North End on loan until next summer, whilst academy duo Joe Rothwell and Ben Pearson will both be representing Barnsley in League One.

Plenty could - and in my opinion, should - be added to that list, not least including Paddy McNair, Tyler Blackett, Jesse Lingard, Andreas Pereira, Sam Johnstone, Guillermo Varela and Nick Powell. One could even argue Belgian wizzkid Adnan Januzaj would benefit from a short spell at another club, having struggled for form under Louis van Gaal last season.

Of course, there's still over a month of the transfer window remaining and many loan deals end up being confirmed in the summer's final hours. But in the interests of partaking in a full pre-season to ensure match fitness and familiarity with their adoptive clubs, United's youngsters are better off securing loan moves as soon as possible.

MORE FIREPOWER?

Manchester United v Manchester City - Barclays Premier League

Louis van Gaal clearly has faith in Wayne Rooney as his first-choice centre-forward for next season, claiming he's capable of matching Sergio Aguero's 26-goal tally to claim the Premier League's Golden Boot.

Yet, the Manchester United skipper hasn't exactly enjoyed a superfluous run of the goals over the last three seasons, his last 20-goal campaign coming all the way back in 2011/12.

The argument that the 29 year-old has spent as much of his time since in midfield as up front certainly has some substance to it, but Rooney still isn't a player you'd define as a natural goalscorer, in the same manner as Aguero, former team-mate Robin van Persie or Chelsea's Diego Costa.

In my opinion, the Red Devils need a bit more firepower to clinch next term's title. The striker market is hardly booming at the moment, with the likes of Jackson Martinez, Carlos Bacca, Paulo Dybala, Mario Mandzukic and Christian Benteke already completing big money moves this summer, but there are still a few options out there.

Zlatan Ibrahimovic, for example, is probably the best stop-gap solution United could ask for at the age of 33, with his PSG contract now into its final year. Likewise, Robert Lewandowski's agent believes Bayern Munich would only sell the Poland international - famed for once netting four past Real Madrid at the Bernabeu - for in excess of £35million which, in the grand scheme of things, is hardly an unjustifiable sum.

GET PEDRO BEFORE SOMEBODY ELSE DOES

There may not be a better value-for-money player on the market this summer than Barcelona's Pedro.

The winger-forward has done it and won it all throughout his tenures with the Catalans and the Spanish national team, winning five La Liga titles, three Champions League titles, a World Cup and a European championship, and at 27 years of age is still firmly within his footballing prime.

In my opinion, the 5 foot 7 attacker would be the ideal replacement for apparently PSG-bound Angel Di Maria and with a release clause of just £22million, he's well within the Carrington outfit's financial reach.

Manchester United are reportedly leading the race to sign the 51-cap international but they need to get a move on. World-class players without world-class price tags don't come around too often, so the majority of Europe's top clubs will be more than happy to take advantage of any hesitancy from the Red Devils.

DECIDE WHEN DE GEA SHOULD LEAVE

Manchester United have been playing hardball regarding Real Madrid's lengthy pursuit of David De Gea, insisting that they'll only part with the PFA Player of the Year nominee if they get Sergio Ramos in return.

But with Ramos set to sign a new deal at the Bernabeu and Los Blancos already signing Kiko Casilla as Iker Casillas' replacement, suddenly the Red Devils have lost pretty much all of their leverage around the negotiating table - which is a huge issue, considering De Gea's contract expires in a year's time.

United are in a position where they can probably afford to lose De Gea on a free transfer; they're one of the few clubs in world football who don't have to worry about Financial Fair Play and thus many would argue another season with the world-class Spaniard between the sticks probably trumps the incentive of accepting a £30million bid from the European champions.

But at the same time, if United do want a return on the 24 year-old - let's face it, allowing world class players leave on free transfers hardly makes financial sense or sends out a particularly positive message to the fan base - they've only got a month to broker a deal, with Real more than happy to wait until next summer.

Likewise, the Old Trafford outfit don't have long left to find a viable replacement. Louis van Gaal has already revealed back-up goalkeeper Victor Valdes will be sold this summer after refusing to play for the reserves. Netherlands No.1 Jasper Cillessen has been strongly linked but many would prefer to see Tottenham's Hugo Lloris between the Old Trafford sticks next season.