Since Roman Abramovich took over Chelsea in 2003, the Blues have become a powerhouse not just in England but also in Europe. The club has won five Premier League titles and two Champions League trophies along with numerous domestic cups under his ownership.The Russian has pumped a lot of money into transfers and has brought several big stars to Stamford Bridge. The likes of Didier Drogba, N'Golo Kante and Eden Hazard all arrived for hefty sums but made their transfer sums look like a drop in the ocean with their performances.Chelsea have also overpaid for several players in the pastWhile the transfer sums for the aforementioned players seem pretty low compared to their performances, the same cannot be said about the other big-money signings at Chelsea. These players arrived at the club for huge sums, but their performances did not justify their transfer fees with many people feeling that the Blues overpaid for them.Here, we take a look at five such players for whom Chelsea ended up overpaying in the transfer market:#5 Tiemoue Bakayoko - £36 millionChelsea v AFC Bournemouth - Carabao Cup Quarter-FinalTiemoue Bakayoko was a key part of the famous AS Monaco side that won the Ligue 1 title in 2016-17. However, signing him for a whopping £36 million proved to be a huge mistake by Chelsea.The midfielder arrived in London with huge expectations and was seen as the perfect replacement for Manchester United-bound Nemanja Matic.He started well for the Blues, but as the season progressed his performances started to dwindle. He looked decent in patches, but never really fulfilled his potential or justified his price-tag at Chelsea.Bakayoko did manage to make 24 Premier League starts in 2017-18, but it was clear after Maurizio Sarri's arrival that he did not fit in. As such, he was sent out on loan to AC Milan to accommodate new signing Jorginho in midfield.The Frenchman was later sent out on loan back to Monaco, then Napoli and is now back at AC Milan again but is surprisingly still a Chelsea player.Goal News@GoalNewsDONE DEAL: Tiemoue Bakayoko joins Milan on loan from Chelsea for the second time 🤝9:07 AM · Aug 30, 20213596161DONE DEAL: Tiemoue Bakayoko joins Milan on loan from Chelsea for the second time 🤝 https://t.co/3pgljQfNpR#4 Alvaro Morata - £59 millionChelsea v Huddersfield Town - Premier LeagueAlvaro Morata arrived at Chelsea for a then club-record fee of nearly £60 million in 2017. It definitely looked a tad punchy for an individual who, while talented, wasn't deemed good enough to be a regular starter for Real Madrid. And Morata certainly proved that he wasn't worth that much with his poor performances on the field.Morata started brilliantly for the Blues with seven goals in his opening eight games under Antonio Conte, including a hat-trick against Stoke. But then it all began to slowly unravel and collapse for the Spaniard.Unable to settle in London, he infamously said he found the city "stressful" and couldn't see himself living in the capital for long. The excitement around him slowly began to fade and his performances also began to suffer. This forced Chelsea to bring in Olivier Giroud in the January transfer window of 2018.The Sun - Tottenham@SunTottenhamTottenham are reportedly keen on Chelsea flop Alvaro Morata to replace Harry Kane next summer7:48 AM · Oct 13, 2021Tottenham are reportedly keen on Chelsea flop Alvaro Morata to replace Harry Kane next summerhttps://t.co/N3VfPhPe9GMorata scored just 15 goals and assisted six in 30 starts across all competitions in his debut season. His poor finishing and lack of confidence in front of goal continued in the second season as he scored just five goals before being sent on loan to Atletico Madrid in January 2019. The move was made permanent in the summer of 2020 with Chelsea recouping around £32 million for the forward.