The biggest transfer of the window without a doubt was Manchester United capturing Juan Mata from rivals Chelsea. The Red Devils probably couldn't believe their luck to see Jose Mourinho so willing to do business, and neither could many others. When Mourinho arrived and dropped Mata it was questionable, but you always expected he would come to his senses and fit the Spaniard back into his side at some point. But Mourinho's commitment to Oscar and Eden Hazard meant there was firmly no place at the inn for Mata, and he's now found a place somewhere else. Chelsea will regret this: he's a brilliant player and although United aren't having a good season, they'll be back at some point soon, which is when Mata will strike and hurt his former club right at their core, and prove that the decision to sell, and to a rival, no less, was a huge mistake. It would have been stupid to sell him to anyone but to give him to arguably the biggest club in England is just ridiculous - this is after all the same club that wouldn't loan Arsenal Demba Ba in the Summer and it raises questions about a certain Wayne Rooney.