Middlesbrough are gearing up for what could be a pivotal transfer window.

The Teessiders will be hoping that some strong new additions will be just what the doctor ordered as Neil Warnock's side push to be considered as promotion frontrunners next season.

Of course signing big-name players isn't a new thing at the Riverside Stadium.

Middlesbrough have spent vast sums over the years on some monumental signings such as Juninho, Fabrizio Ravenelli, Mark Viduka and more.

But for every legendary signing there's at least one who failed to meet expectations.

With that in mind we've pulled together a list of nine signings who flopped after arriving at the Riverside Stadium.

The winger completed his move to Middlesbrough in September 2015, but even his arrival didn't go to plan.

A minor car accident on the way to the airport in Uruguay saw his move delayed and from that point things just didn't really work out for De Pena.

He was limited to just 10 first team appearances in almost two years with the club, creating just one goal in the process.

In July 2017 his contract was terminated by mutual consent before going on to join Real Oviedo.

Now with Dinamo Kiev, De Pena has been competing in the Champions League with the Uruguayan seemingly finding a way to fulfill his potential after leaving the Riverside.

The Dutch winger was Middlesbrough's first signing after securing promotion to the Premier League in 2016.

A fee of £4.5million seemed like decent value at the time with Fischer expected to go on and make a big impact at the club, but unfortunately it just didn't work out.

Fischer made 16 appearances for Middlesbrough during the 2016-17 season, creating three goals in the process.

With the Teessiders suffering relegation that term the Danish star moved on that summer to join German side Mainz for a fee of £2.7million.

Considering his lack of impact and the fact that he was sold at a loss, it's no surprise that he's deemed a flop.

One of the stranger transfer stories to come out of Middlesbrough in the last 20 years.

The year was 2004 and the Teessiders were in a wonderful spell after winning the Carling Cup and preparing for their first ever European campaign.

With Juninho and Doriva on board the club completed a deal for another Brazil international, Ricardinho, who arrived at the club with a big reputation in his homeland.

Unfortunately the midfielder didn't even make a first team appearance for the club and was limited to reserve team action before leaving the club for Brazilian side Santos where he quickly established himself back in the Brazil national set-up.

Mind-boggling doesn't even cut it.

Fans can be forgiven for getting excited at the prospect of signing an international striker who would go on to be the record goalscorer in the K League.

Well Lee Dong Gook certainly left fans baffled after arriving at the Riverside Stadium.

The South Korean attacker joined Gareth Southgate's side in January 2007 on an 18-month contract but struggled to make any real sort of impression during his time with the club.

The attacker went on to make 29 appearances for the club over those 18 months but failed to find the net in the Premier League and netted just twice against Northampton and Mansfield Town before heading back to Korea.

In typical fashion Lee Dong Gook starting banging them in for fun upon his return to his homeland. Standard.

Undoubtedly one of the more talented players to join Middlesbrough.

Unfortunately for the Teessiders it would prove to be an incredibly bad deal when they signed Mido from Spurs from an estimated £7.9million.

Mido was contracted to Middlesbrough for three years but only managed 32 appearances in that time scoring eight goals.

Fitness was a real issue for the Egyptian who arguably spent more time out on loan than he did at the Riverside before leaving to head back to his home country in 2010.

Considering the sum that was spent there's no doubt that this was not a good investment.

We couldn't have a list of Middlesbrough flops without including Afonso Alves, could we?

After banging in goals for fun with Dutch Eredivisie side Heerenveen there was real excitement when the Teessiders forked out £12million to sign the Brazilian in January 2008.

But when a banner reading 'Boro's goal machine' is unveiled before he's even kicked a ball there's always going to be a nervy feeling.

Alves struggled for consistency during his time at the club but did have a few sparkling moments including a brace against Manchester United and a wonderful free-kick against Tottenham Hotspur.

But 13 goals in 49 appearances wasn't enough for expectant fans - especially when he was sold for a significant loss just 18 months later.

The midfielder was regarded as one of the hottest prospects in France when he arrived at the club in 2008.

Unfortunately Digard failed to make a positive impact at the club after being part of the side who suffered relegation in his first campaign with the club.

In the Championship his opportunities were limited under Gordon Strachan and so he joined Nice after 18 months with the club.

At the end of that season he was sold to the French side for a significant loss after making just 36 underwhelming appearances for Middlesbrough.

It was a shame for Digard that he was unable to fulfill his potential but a small comfort for Middlesbrough was that he failed to impressed in the years that followed too.

We could have picked plenty of Gordon Strachan's signings, but there's no doubt that Kris Boyd was the worst of the bunch.

After scoring goals for fun with Rangers it was hoped that Boyd would quickly become one of the best in the Championship after completing a free transfer to the club in 2010.

Boyd was on significant wages and so expectations were high but a lack of goals and an even bigger lack of effort on the pitch left supporters feeling frustrated before he left the club to join Nottingham Forest on loan later in that campaign.

In the striker's only season with Middlesbrough he scored six goals in 29 appearances before leaving the club for Turkey the following summer.

Boyd then struggled to get his career back on track as he saw out his career between Turkey, the USA and Scotland.