Cristiano Ronaldo (Juventus)
Madrid president Florentino Perez sanctioned the transfer of Ronaldo - the club's highest ever scorer - to the Bianconeri in a €100 million deal.
Calderon, who was president at the time of Ronaldo's then world record move to the Spanish giants in 2009 said it was near impossible to replace the Portuguese forward.
Ronaldo brought an end to a spectacular nine-year spell at the club when joining Juventus scoring an incredible 451 goals in 438 appearances winning eight major titles.
"Juventus have concluded a great deal, Calderon said. Brilliantly done by chairperson Andrea Agnelli. Real Madrid will lose a lot, it was a big mistake.
"Perez tried to save face but it was too late, Cristiano refused his offer as the problem was no longer a financial one."
"The club value of Juventus is going to see sharp improvements," Calderon added. The money spent on Cristiano will be recouped faster than most people expect. Sponsorship deals will now be dealt with differently and the revenues will increase."
Calderon then predicted that the five-time Ballon d'Or winner would continue his incredible goal-scoring record in Italy.
"How do I see Ronaldo in Italy? Scoring 40-50 goals a season and winning more titles.
"Cristiano's secret? He wakes up every day to outdo himself. He is an exemplary professional, in an unparalleled way. The most decisive player in the world."