Chelsea are known for signing players in the January transfer window. The Blues have often found the need to secure mid-season deals for players. This could also explain why they have been one of the most successful clubs in Europe over the past decade.Chelsea have had a mixed bag of success in the January transfer windowSince Russian oligarch Roman Abramovich took ownership of the club, Chelsea have been shelling out the cash for fun. In doing so, the club has sometimes missed the mark, especially in the winter transfer window. Clubs are normally reluctant to let their best players or prized assets leave and are more open to moves in the summer.Telegraph Football@TeleFootballWho are the best and worst Chelsea January signings? @Matt_Law_DT delivers his verdicttelegraph.co.uk/sport/football… http://t.co/HA3fd4MELy5:10 AM · Jan 30, 201531Who are the best and worst Chelsea January signings? @Matt_Law_DT delivers his verdicttelegraph.co.uk/sport/football… http://t.co/HA3fd4MELySimilarly, the January transfer window is mostly used to sign players in particular positions. There are often season-ending injuries and various other issues with players. In order to cover for them temporarily or permanently, clubs try to secure cut-price transfers.Chelsea have always tried to sign the best players, irrespective of money or the time of the year. They have found success in doing so, as evidenced by the signings of David Luiz, Gary Cahill, Nemanja Matic and several others.However, they have not always nailed their transfer targets and there are some regrettable examples in that list as well.On that note, let's take a look at the 5 worst January signings in the history of Chelsea Football Club.Note: players signed on loan are not being considered #5 Fernando Torres (2011-2015)Vitesse Arnhem v Chelsea - Pre Season FriendlyFernando Torres is somebody who created both good and bad memories for Chelsea fans. The Spaniard was one of the best strikers in the world at Liverpool and had scored 81 goals in 142 appearances for the Reds.Following his 2010 World Cup victory with Spain, Chelsea broke the British transfer record to sign him in January of 2011 for £50million.The Blues won the 2009-10 Premier League title and were gearing to make it two in a row. Signing Torres felt like the cherry on top of the cake at the time.GOAL@goalLiverpool knew Fernando Torres would be a flop at Chelsea according to Jamie Carragher 7:47 AM · Apr 23, 202044143Liverpool knew Fernando Torres would be a flop at Chelsea according to Jamie Carragher 😲 https://t.co/WLpvCD9J5EHowever, it all turned sour very quickly. Torres only managed a single assist in the 15 appearances he made for the Blues for the remainder of the campaign. His miss in front of a virtually open goal against Manchester United in a crucial fixture led to critics labeling him a 'flop'.Things did not change the following season, but Torres did manage to become a fan favorite. He scored the goal that gave the London club the edge over Barcelona in the 2011-12 UCL semi-final– a competition they went on to win for the first time in their history.In the years that followed, Torres proved to be a vital player in the 2013 Europa League triumph. However, he never managed to become an elite goal-scorer at Stamford Bridge.The Spaniard was eventually sold to AC Milan in 2015. Torres retired a couple of years ago and still shares a good relationship with fans of the club. However, given the money spent on him back in the day, it can be argued that 'El Nino' was a transfer failure.#4 Scott Parker (2004-2005)Fulham FC v Chelsea FC - Premier LeagueScott Parker had a short-lived career at the West London club. One of the first signings of the Abramovich era, the midfielder arrived in January of 2004 as a promising prospect from Charlton Athletic. Although he was not afforded too many chances in the 2003-04 campaign, he went on to win the PFA Young Player of the Year that season.Soccer AM@SoccerAMSlaviša Jokanović was Claudio Ranieri’s first Chelsea signing and Ranieri went on to replace him as Fulham manager. Now Claudio Ranieri has just been replaced by caretaker boss Scott Parker, who was his last signing as Chelsea manager. 🤓🤓10:38 AM · Feb 28, 201965611633Slaviša Jokanović was Claudio Ranieri’s first Chelsea signing and Ranieri went on to replace him as Fulham manager. Now Claudio Ranieri has just been replaced by caretaker boss Scott Parker, who was his last signing as Chelsea manager. 🤓🤓 https://t.co/mBkd9BOECIJose Mourinho arrived the following campaign and the Portuguese manager had his favorites. Claude Makelele, Frank Lampard and new signing Tiago Mendes formed the base of midfield, a position Parker always hoped he would develop in. He was handed limited minutes and was often considered a bit-part player at the club. Parker's lackluster performances as a substitute also did not help his case.The Englishman eventually departed Stamford Bridge at the end of the 2004-05 season but was a part of the team that won the Premier League title that season. Following this, he joined rivals West Ham United and then moved to Tottenham Hotspur.Parker played a part in intense derby games against the Blues, further ruining any chances of fans having happy memories of him. So, even though the Englishman did not stay all that long, Chelsea are unlikely to count him as a successful signing by any stretch of the imagination.