Juan Mata is expected to complete his £37m move to Manchester United today - but the question is: will Chelsea manager Jose Mourinho regret selling the Spanish playmaker to a rival club?
After all, Mata has been crowned Chelsea's Player of the Year for the last two seasons running, is still only 25, and has proven that he can play a match-winning role in pivotal Premier League matches.
Many suspect that Mourinho will live to regret his decision. But the job of a manager is to do what he thinks is best for his team - and the Portuguese coach's decision has been reluctantly accepted by the majority of the Blues' faithful.
However, if the 10 transfers on this list are anything to go by, the Chelsea manager could be making a very big mistake...