8. Juan Mata
Shuji Kajiyama/AP/Press Association ImagesJuan Mata became Manchester United's most expensive signing in history in the January transfer window after completing his £37.1 million move from Chelsea. However, given the difficult time he endured under David Moyes and the fact he will not be playing in Europe at all next season while his former club grace the Champions League, he may be regretting that decision. United finished seventh under Moyes, did not even qualify for the Europa League, and look as though they are going to go through an uncertain period again next season in spite of their recent signings. By contrast, Chelsea look as though they are building a side capable of winning their first Premier League trophy since 2010 under Jose Mourinho and Mata must be wondering if the grass is really greener at Old Trafford.