#4 Ivan Rakitic (Barcelona)
Whereas most of the players on this list are young, and probably have the best part of their career to come, Ivan Rakitic is a man you could argue is a touch past his best. However, one thing United have suffered from in the last couple of years is that they have lacked experience in key areas, and they have been short of leaders both on and off the pitch. Bringing in someone like Rakitic would help give Solskjaer more control in the dressing room, something that he seemed to lack when things went wrong towards the end of last season.
At 31, Rakitic has won all there is to be won in European football. He may feel that it is time for a new challenge, and he could be someone United can build their side around this season. The Croatian midfielder may find his opportunities limited this season, after Barcelona spent big on Frenkie de Jong, and the time may be right for him to leave the Nou Camp.