Calderon, the former president of Real Madrid is frequent in the media and often gives an insight into his former club.
When Florentino Perez was elected as the president, the signing of Cristiano Ronaldo had already been completed by Real Madrid.
The forward completed a world-record switch worth £80million to the Bernabeu in the summer of 2009.
Ronaldo had already won the Champions League and three Premier League titles before he got his move.
The deal was closed by Calderon before his departure and 75,000 fans turned out to see Ronaldo’s unveiling.
“Cristiano had the illusion to change, he wanted to come to Real Madrid, he was very motivated to come here because the club brought him a lot from the personal point of view, he wanted to win more titles and succeed here,” he said.
“They were a year and a half of hard negotiations, but Manchester finally had to accept the offer of £80m.”
Calderon them claimed that Perez was not fully convinced by Ronaldo and praised him for letting the Portuguese prove his worth.
“For me it was a relief that Florentino signed him and did not give up on him, because before signing for Real Madrid, the president said that Cristiano was overrated,” he continued.
Calderon also claims that the Juventus star heard about Perez’s verdict and was not happy.
“Cristiano learned about this and even said he was giving up the £30m [fee that had to be paid of the deal collapsed],” he added.
“He did not understand how Florentino could I was doubtful about him and there started a disagreement that lasted nine years, finally the player came because his environment convinced him.
“Jorge Mendes called me and told me that he finally got the signing for which I had fought so much.”
Sir Alex Ferguson was desperate to keep hold of Ronaldo at United, but Real Madrid tabled an offer they simply couldn’t resist.
“To sign Cristiano, we talked to Manchester for my good relationship with the leaders, but with Ferguson not because he did not want to know anything about Cristiano wanted to come to Real Madrid,” he added.
“Finally they convinced him because his leaders told him it was best for both parties, he had to have come a year before, but finally we decided that way.”
Ronaldo showed Los Blancos what they were missing in midweek when he scored a hat-trick to knock out Atletico Madrid in the Champions League.