10. Juan Sebastian Veron
Bought for: £28.1m by Manchester United in 2001
Sold for: £15m to Chelsea in 2003
Manchester United manager Sir Alex Ferguson thought Veron supreme was the long-term answer to a lack of creative impetus in midfield when he signed the Argentine playmaker, but despite showing flashes of brilliance the ex-Lazio schemer never quite settled at Old Trafford.
Two seasons of frustration filled with the odd piece of Champions League magic were not enough to convince Ferguson the midfielder was worth keeping though, as the Red Devils decided to take a huge hit on the misfiring star and sell him to domestic rivals Chelsea for just a little more than half of their initial outlay.