#4 Mateja Kezman (2004-2005)
A lot was expected of Mateja Kezman, the then Yugoslavian pocket dynamo, following his transfer to Stamford Bridge from Dutch giants PSV.
Pacy, direct with a low centre of gravity and deadly finishing, it was expected that the pocket dynamo would be tailor-made for the helter-skelter world of English football.
He had scored 35 goals in the 2002/2003 season in the Eredivisie as PSV won the title and seemed the goleador that the Blues really needed to kick-start the Roman Abramovich era.
It turned out to be a disaster of epic proportions as Kezman looked hopelessly out of his depth as the team's Arrowhead. While he wasn't helped by the conservatism and constant tinkering of then manager Claudio Ranieri, the striker looked like a deer caught in headlights and in his only full season in England; he hit the net 7 times in 41 matches.
A season later, he was sold to Atletico Madrid for £5.3 million, the same amount for which he was bought.