(CNN) -- Kevin-Prince Boateng signing for Barcelona in the January transfer window caught many people by surprise.

During a long season, January is the only opportunity clubs -- whether they are fighting for honors or battling relegation -- have to strengthen their squads.

However, historically the January window has proved a tricky time to buy players that go on ad make an impact.

"There are plenty of teams who ostensibly strengthened their squad, but ended up doing worse after January," according to a 2017 study by Omar Chaudhuri, Head of Football Intelligence at 21st Club, a company that uses data to "help football clubs achieve competitive edge and build sustainable success."

"Brute force spending alone is unlikely to work, given it might only be worth one or two extra points if we follow historical trends," added Chaudhuri.

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So with managers struggling and owners panicking at this time of year, some of the strangest transfer scenarios have emerged.

With this in mind, here are five of the weirdest January transfers.

Spoiler alert ... Most were a mistake ...

Kevin Prince-Boateng

(Sassuolo to Barcelona)

Lionel Messi, Luis Suarez and Philippe Coutinho -- Barcelona boasts a plethora of world-class attackers. And now the Catalan club can now add a new name to the list, former Tottenham and Portsmouth forward Boateng.

He'd been plying his trade at Serie A team Sassuolo -- the ninth club he'd played for in an itinerant career. Then the call came from the Camp Nou and Barcelona quickly agreed a loan deal for the 31-year-old with the option to buy at the end of the season for $9 million.

Safe to say, the former Ghanian international looked rather surprised but there is a method to the madness, according to Barca.

The club says Boateng is "versatile to a fault." He's had experience playing as a traditional striker, playmaker and as a central midfielder and featured in four of Europe's top leagues and scored goals wherever he's been as well as winning the Serie A title with AC Milan in 2011.

Julien Faubert

(West Ham to Real Madrid)

There were many raised eyebrows when one of the world's biggest clubs came in for Julien Faubert in 2009.

The Frenchman had struggled at English Premier League side West Ham, failing to score a single league goal in his first two seasons at the club.

But it seemed Real Madrid saw something everyone else didn't, signing the attacker on a six-month loan deal.

It proved an ill fated transfer with Faubert unable to emulate the Galacticos that went before him.

He made just two appearances for the La Liga side and failed to score a single goal. He even fell asleep while on the substitute's bench during a match.

Kim Kallstrom

(Spartak Moscow to Arsenal)

When injury struck, Arsenal turned to veteran midfielder Kim Kallstrom in January 2014.

The veteran Swede certainly had the midfield experience to help the English side but there was a slight problem -- he had a broken back.

Undeterred, then manager Arsene Wenger went through with the decision to sign the midfielder on loan.

Struggling with his fractured vertebrae, Kallstrom made just four appearances at the Emirates before returning to Spartak Moscow.

Despite his misfortune, Kallstrom said he enjoyed his time at Arsenal and the love is strangely reciprocated by the club's fans.

Fernando Torres

(Liverpool to Chelsea)

When Fernando Torres signed for Liverpool, the Spanish striker took the English Premier League by storm, scoring 81 goals in 142 appearances for the Anfield club.

However, after suffering a serious knee injury in 2010, the speed that once made him so lethal seemed to desert Torres, whose confidence was also hit.

Even so Chelsea decided to take a chance on Torres -- paying an estimated $64 million for his services in January 2011.

Despite winning the FA Cup, UEFA Champions League and the UEFA Europa League during his spell at Stamford Bridge, Torres never got back to his best and struggled to cement himself in the first-team.

He left the London club a shadow of his former self but went on to rebuild his career in La Liga and now Japan.

Andy Carroll

(Newcastle to Liverpool)

In one of the most exciting transfer deadline days in English Premier League history, Liverpool signed Andy Carroll for $45 million in 2011 as Torres headed to Chelsea.

It was a transfer fee that took many by surprise and one that his club Newcastle United couldn't refuse.

Carroll was signed on the same day as Luis Suarez -- for $15 million more -- who went on to score 82 goals for the club.

While the Uruguayan prospered, Carroll scored just 11 goals in 58 appearances for the club and left in 2012 for West Ham.

He's since struggled with persistent injuries but since England international Harry Kane suffered an ankle injury, there have been rumors Carroll could be headed to Tottenham.