5) Juan Mata
A player who perhaps hasn’t hit top form since his eagerly-anticipated move from Chelsea last January, Juan Mata has been linked with a move to Atletico Madrid this January. Although Louis van Gaal seemingly has some big-name targets lined up as replacements, it’s hard to understand why the club would let an expensive signing and proven quality player at his peak leave for considerably less than they paid for him. Not fancied by Jose Mourinho, it may be that Mata is being under-rated by van Gaal as well, but the Spaniard is a creative talent that can make a big difference and not one you’d want to pass on to another top club.