Reports in Spain suggest that talks with Tottenham about a deal for the Welsh winger are ongoing after the Madrid club made a world record bid for the player's services.
And now ex-Real chief Calderon suggests Madrid's determination to bring Bale on board is in part motivated by concerns over Ronaldo's unhappiness in Spain.
Gareth Bale's move to Madrid could allow Cristiano Ronaldo to leave
Cristiano Ronaldo wants a pay rise at Madrid
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Perez told talkSPORT: "I know that he is not happy at all with the attitude and behaviour of the president. He is asking for €20million (£17.5m) net every season which is going to be difficult for Real to accept.
"I think the president has all his eggs on the table just in case he can’t get the renewal of Cristiano. That is my impression.
"He’s afraid at some moment that Cristiano will say, 'I am not going to go on'. That will be bad news for Madrid. I would like to see him retire at Real but now the situation is difficult. Let's see in the next weeks or months if it can be sorted out and he can stay."
Ramon Calderon says Florentino Perez is concerned about Cristiano Ronaldo leaving
Florentino Perez is chasing Gareth Bale hard
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Florentino Perez's relationship with Cristiano Ronaldo has soured
Ronaldo has been linked with a return to Old Trafford throughout the summer, and it had been reported that Manchester United would be willing to meet Madrid's £80m valuation of the player.
But whether the Red Devils would be in any better position to meet Ronaldo's wage demands, or whether the 28-year-old would be willing to reduce his demands to push through a return to England, remains to be seen.
David Moyes would love to bring Cristiano Ronaldo back to Old Trafford