#9 Tiemoue Bakayoko (2017, €40 million)
Signed in the summer of 2017 to partner the ever so reliable N'Golo Kante, Tiemoue Bakayoko signed for Chelsea after the Blues won the battle to his signature over Manchester United. The French midfielder was one of the most sought after players in the market at the time and famously teased the Red Devils on social media, before eventually signing for Chelsea.
Described as a proper modern-day box to box midfielder, Bakayoko made a name for himself in his home country, as he played a pivotal role for Monaco in their sensational title-winning season in 2016-17. In England, however, he looked a shadow of his former self and experienced a torrid time with the Blues, as Chelsea as a whole fell flat in the 2017-18 season.
He was shipped off to AC Milan on loan for the forthcoming, where he experienced a renaissance of sorts, before returning to Monaco on loan for the current campaign. Bakayoko remains 9th on Chelsea's list of record signings and it remains likely that the Blues will cut their losses and sell him in the summer.