Ten worst Chelsea transfer gaffs, including £50m flop Fernando Torres & Daniel Sturridge sale to Liverpool

5) Romelu Lukaku

Another player Chelsea should have held on to, Romelu Lukaku has been allowed to make the £28m move to Everton this summer after spending the last two seasons out on loan. One of the most promising young players in the world, it is hard to understand why Mourinho opted to sell the 21-year-old in favour of bringing back the 36-year-old Didier Drogba to Stamford Bridge. Like Mata, this sale will surely come back to haunt Chelsea in the near future.