6) Khalid Boulahrouz (August 2006, £6m)
The Dutchman was once described as the perfect cover for all Chelsea’s defensive options, but he never lived up to his billing. Chelsea’s defence was consistent and was rarely altered, while injuries further restricted his opportunities to play in the first-team.
5) Mateja Kezman (July 2004, £5.3m)
Managed just seven goals in 40 games for the club, departing after his one and only season. He struck 129 goals in 176 games for former club PSV Eindhoven, but was never able to live up to that reputation in a blue shirt, although he did manage a goal in the Carling Cup final.
