Manchester United might still be the most successful club in Premier League history, but that doesn't mean they're immune to absolute shockers in the transfer window.

If anything they've been one of the biggest culprits when it comes to buying flops over the years. Even Sir Alex Ferguson, one of the most decorated managers in football's entire history, bought some very questionable names during his tenure.

Since Fergie's retirement, the likes of David Moyes, Louis van Gaal and Jose Mourinho have all managed to add to the list of Man United flops with their questionable recruitment.

But which players will go down as Man United's biggest flops in the Premier League era?

We've had a go at selecting 20 and we think most United fans will agree with these...

Morgan Schneiderlin

First up is a midfielder who you may have forgotten even plied his trade at Old Trafford - current Everton and ex-France man Morgan Schneiderlin.

United tried to follow in the footsteps of their rivals Liverpool by poaching some talent from Southampton when they paid an eye-watering £25m for Schneiderlin in the Louis van Gaal era, but unlike the Sadio Mane's and Virgil van Dijk's, this Saints star was to flop at a much bigger side.

William Prunier

How could we leave Willian Prunier off this list?

When he was on the field Sir Alex Ferguson's Red Devils would have been no worse off with an actual statue in central defence.

The former France international, somehow, is widely regarded as one of the worst players to ever ply his trade at "The Theatre of Dreams" and he's now managing in France's fifth tier.

Gabriel Obertan

Signing Gabriel Obertan for his all-star Old Trafford team and spending actual money on him, too, was hardly one of the Fergie's masterstrokes - and it's not the first time you will see the legend get his recruitment woefully wrong in this list.

The hapless winger made just 27 appearances in his four-year United career, scoring a mere one goal and only registering four assists, he did get a Premier League winners' medal though.

Radamel Falcao

Radamel Falcao was hardly the first player to come to England with a huge reputation in European football and prove he's not even near English top-flight standard, and he surely won't be the last either.

Having scored bags of goals on the continent for the likes of Porto, Atletico Madrid and a resurgent Monaco team, the Colombian was given his big chance to shine in the Premier League on loan in Manchester for the 2014/2015 season.

Needless to say that he didn't take it, with the striker finding the back of the net on four occasions and he even got another opportunity with Chelsea the campaign after, to show everyone once again how below-par he is in England.

Zoran Tosic

The picture above rather sums up Zoran Tosic's time in west Manchester - the Serbian was surrounded by some wonderful players such as Michael Owen, Paul Scholes, Rio Ferdinand and more - and he was somewhat the odd one out.

This was because, like so many in this list, Tosic simply never had the ability to be a star at the world's biggest club and that's why he lasted only one term after joining from Partizan Belgrade in 2009.

Wilfried Zaha

Manchester United may well now regret letting go of Wilfried Zaha for well under £10m just four years go, however, this doesn't take away from the fact that he wasn't good enough for them.

£10.58m plus add-ons was a lot of money back in January 2013 and that's exactly what David Moyes paid to capture him from Crystal Palace, only for the Ivory Coast international to appear on four unmemorable occasions - now Zaha is once again knocking on the door of a move to a "Big Six" side having come on leaps and bounds since then.

Memphis Depay

Louis van Gaal should have been more cautious knowing how many attackers purchased from his native Netherlands have struggled to adapt in England after thriving over there.

Look up Dutch Premier League flops in the dictionary and Depay's name will appear.

Massimo Taibi

Few members of this list have an iconic moment in a Man United shirt to their name, although we must confess Massimo Taibi's is seminal for the wrong reasons.

Having impressed on his debut against Liverpool after replacing Peter Schmeichel in the summer of 1999, the Italian let Matt Le Tissier score with one of the tamest efforts in Premier League history against Southampton a game later, and barely featured again.

Angel Di Maria

It's hard to overlook our next United failure when it comes to the title of the biggest club-record signing dud in world football ever - Angel Di Maria.

To be fair to the Argentian, though, he's since shown his true quality at Paris Saint-Germain.

However, under the weight of a £59.7m transfer from Real Madrid ahead of the 2014/2015 term, the Argentina star failed to make himself worthy of the famous Red Devils number seven shirt, providing little more than an eye-catching lob away at Leicester City.

Diego Forlan

A case of De Ja Vu here with Di Maria's fellow South American Diego Forlan, a player that seemed to do extremely well at pretty much every club in his career apart from Man United.

Forlan was so bad at Old Trafford that it was laughable, as he somehow managed to rack up close to a century of matches under Fergie, who probably didn't want to lose face after splashing out £6.9m on him, which was a large sum of money in 2002 football.

Paul Pogba

Paul Pogba's inclusion is bound to upset some people.

But the fact remains that Jose Mourinho's Red Devils broke all kinds of records in forking out £89.3m to prize the Frenchman away from Juventus and back to his boyhood side, that was three years ago and he's only been able to produce his best in drips and drabs, and gotten himself involved in countless off-field controversies since.

Maybe, one day, Pogba will make the list of better United arrivals, though it must be said that hardly looks likely at the moment.

Alexis Sanchez

Why Alexis Sanchez turned out to be such a poor player for the Red Devils remains a mystery, perhaps it was the now seemingly-cursed number seven shirt?

Seriously, though, he had established himself as one of the most exciting players in the Premier League at Arsenal and there was no reason why he couldn't be the same when he swapped north London for Manchester.

There was, however, one small consolation for United - they never wasted any money on Sanchez, they just gave up Henrikh Mkhitaryan, who was hardly a success story after a big-money move from Borussia Dortmund, in a swap deal.

Juan Sebastian Veron

Known as "The Little Witch" for his devilish trickery in the centre of midfield, Juan Sebastian Veron arrived at "The Theatre of Dreams" as one of the best on the planet in the most expensive transfer in British history at the time.

Despite a cracking start to life in the Premier League and Fergie's constant and at-times ferocious backing of him in the media, the Argentine couldn't find the football that had earned him such a huge reputation in Italy and moved on two years later as one of the original examples of the English top-flight's superiority over all other leagues and the international game.

Owen Hargreaves

The tale of Owen Hargreaves and Manchester United is a slightly different and much sadder one as the England midfielder, who made his name at Bayern Munich, was probably good enough to make hundreds of appearances at Old Trafford.

In reality, Hargreaves only ever featured 39 times for the Red Devils and this was down to a horrible injury plague that never seemed to leave him alone after moving back to his native land.

Although, putting sentiments aside, the figures mean Hargreaves simply has to appear in this list.

Bebe

It's hard to think about everything Sir Alex Ferguson achieved at Old Trafford without also recalling the time he took a gamble on a Portuguese youngster who, not too long before his move, had been playing football in and practically living on the streets of Lisbon.

Unsurprisingly, what is, without doubt, the strangest signing in United history also turned out to be one of the worst as the winger quickly made it clear that Fergie had made a rare mistake, by playing on only seven occasions in England with very little impact.

Matteo Darmian

Former Serie A prodigy Matteo Darmian was signed by Jose Mourinho in 2015 to be the future of United's right-back position with Antonio Valencia not getting any younger - he was never going to live up to this and having been rejected by AC Milan earlier in his career, Mourinho and the recruitment team should have known.

But what's even more baffling is that Darmian, obviously way short of what was needed, was able to make almost a century of United appearances.

Manucho

There's no other way to describe striker Manucho's transfer to Man United than just strange - Fergie's odd side strikes again!

The tall centre-forward was plucked out of the top division of Angolan football mid-way through his career and thrust into the best league in the world in January 2008, his chances of succeeding so minute that you can guess what happened.

But at least Manucho was able to carve out something of a living playing football in Europe for himself in the end, which is nice.

Kleberson

Famously fooling Fergie and his sometimes hilariously bad recruitment staff with his performances for Brazil at the 2002 FIFA World Cup, Kleberson often looked like a fan who'd won a competition to play in a Man United shirt.

Even more incredibly, the Red Devils were forced to beat off stiff competition from their top European rivals to land his signature for £6.5m in 2003. The likes of Barcelona and Celtic dodged a bullet as the Brazilian never got close to gauging the pace of top European football.

Eric Djemba-Djemba

Nearly 15 years after it ended, all sorts of stories are still coming out from Eric Djemba-Djemba's infamous spell in Manchester, such as his obscene wage and odd nicknames - Eric Cantona being one of them.

And whilst there's no taking away the quality of that unbelievable volley at Elland Road, the Cameroonian was supposed to replace an ageing Roy Keane at "The Theatre of Dreams" and seeing Djemba-Djemba's quality was probably what possessed the Irishman to carry on playing at United until the age of 34.

Anderson

You may have noticed by this stage that the Red Devils really haven't had much luck with one-named players down the years and it's no different when it comes to our 20th and final terrible signing.

It was hoped that supposed Brazilian midfield dynamo Anderson would follow in the footsteps of fellow Portuguese-speaking teammates like Cristiano Ronaldo in west Manchester, he did cost Fergie well over £20m after all.

However, people don't always get what they hope for and in spite of taking to the field in red on 181 occasions, Anderson never really lived up to his potential and that's something of an understatement.