#5 Leonardo Bonucci
Leonardo Bonucci spent two years at Inter Milan where he managed to make just one appearance for the club and he was sold to Treviso. Since the departure of Lucio and Samuel from Inter Milan, they have struggled for a solid defensive figure at the back before the arrival of Miranda from Atletico Madrid.
At the age of 30, Bonucci is one of the best defenders in the world and what is worse is the fact that Inter Milan arch-rivals Juventus and AC Milan have enjoyed the services of Italian international.
Since the time he left Inter Milan he has enjoyed plenty of success winning the Serie A six times, 3 Coppa Italia titles, 3 Italian Super Cups and he twice came very close to winning the Champions League only to be beaten by Barcelona and Real Madrid in the final.
You can't really presume that Bonucci would have become a top player at Inter, but they should have trusted the younger players more considering their old guard needed replacing. But they instead allowed him to leave for cheap, unlike Juventus who made a good profit from selling him to AC Milan.