#1 Andrea Pirlo (AC Milan to Juventus)

When Andrea Pirlo moved to Juventus in 2011, a lot of eyebrows were raised. AC Milan had not only let their best midfielder join their rival, they had also let him leave on a free transfer.
After a prolonged period of trouble for Juventus, Pirlo’s signing came as a breath of fresh air and instilled confidence that the Old Lady could again compete for the globe’s biggest prizes.
Pirlo enjoyed his time in Turin and ended up winning the Seria A in each of his four seasons. He formed a formidable trio with Vidal and Pogba throughout his tenure. He also helped Juventus reach the UEFA Champions League final in 2015.
Under Conte, Pirlo enjoyed a new lease of life, playing as a deep-lying playmaker. He put in scintillating performances week after week and controlled games with his astronomical technical ability.
Pirlo is one of the greatest midfielders to have graced the beautiful game and Juventus pulled off a masterstroke when they signed him for free in 2011.
Signing a midfielder of his quality was a bargain in the truest sense and hence qualifies to be the best free transfer of the 21st century.