The prolific Portugal forward moved to the Spanish giants from Manchester United in 2009 and has since won a La Liga title, the UEFA Champions League and the Copa del Rey twice.
Ronaldo has become the talisman of the Real team over the past five years, leading by example with an incredible goalscoring record, but the man who brought him to Santiago Bernabeu believes the 29-year-old has become disillusioned with the reign of current president Florentino Perez.
Key men Xabi Alonso and Angel Di Maria both moved on in the close-season and, although Real have recruited world-class replacements in Toni Kroos and James Rodriguez, Calderon believes Ronaldo is not happy with the departures.
"My impression is he is fed up with the policy of the current president," Calderon told talkSPORT.
"When he came [to Real Madrid] with [Arjen] Robben he thought he would be a good colleague for him in the team [but then Robben was sold].
"Two years ago it was [Gonzalo] Higuain sold and he didn't like that. Last year he thought it was a mistake to let [Mesut] Ozil leave and the last straw was selling Xabi Alonso and Angel di Maria this summer."
There have been rumours in recent weeks that Ronaldo is keen for a return to United, and Calderon revealed the Portuguese always spoke fondly of his former club.
"When I signed him, I remember he said he was grateful to Manchester United," he said.
"He had a marvellous time there, he likes everything. It is a really great club."
