Reports have suggested that Manchester United are closing in on a move for Chelsea playmaker Juan Mata and, if the twice Blues Player of the Year does end up at Old Trafford, it could have drastic consequences for the Stamford Bridge outfit.
The Red Devils are extremely unlikely to win the Premier League title this season, so the Spaniard could in-fact help take points off Chelsea's title rivals in this campaign.
However, while it may be a good move for the short-term, in the long run, it could backfire as Manchester United will look to get back on top of England's elite division.
So, this seems the perfect chance to look at other transfers that have backfired for the selling club.
Let's take a look at six of the best: