5. Andrea Pirlo – AC Milan to Juventus – Free
What were Milan thinking when they neglected to offer the veteran string puller a new deal in 2011? Believing him to be past his best, Milan got shot of what they thought would be a massive liability only to regret it when Pirlo went on to slot right into a dominant Juve midfield and prove that he is still by far the best midfielder in the county. Oh how Milan could do with him now.

