8- Khalid Boulahrouz (23, Hamburg, £9 million)
When Chelsea signed Boulahrouz in 2006, they hoped they were signing quality central defensive cover for the likes of Ricardo Carvalho and John Terry. Boulahrouz was a highly rated young centre back and it was hoped that he could develop at Chelsea and give competition to Chelsea’s first choice central defensive pairing. However this did not happen and despite the Dutchman being given the no 9 shirt at the Blues, Boulahrouz only made 13 appearances for Chelsea and was sent off on loan to Sevilla after only one season at Stamford Bridge. On his return he was sold to Vfb Stuttgart for half the price that Chelsea signed him for.