William Gallas for Ashley Cole
In August 2006, Chelsea just beat the summer transfer deadline to sign Ashley Cole for a reported fee of £5 million and French centre-back William Gallas.
Gallas - who would later play for another London side in Tottenham Hotspur - did not exactly appear to part Chelsea on amicable terms, while Cole is still very much a detested figure at the Emirates Stadium.
WINNERS - CHELSEA
Despite the England stalwart now seemingly having lost his place in the Chelsea starting XI to Cesar Azpilicueta, he has given eight-years of admirable service at Stamford Bridge and will surely go down as one of the most consistent players in Premier League history.
While Cole has gone on to win another Premier League title, four FA Cups and a Champions League trophy at Chelsea, Gallas won nothing at all at Arsenal and moved to Spurs in 2010.