Former Real Madrid president Ramon Calderon believes Cristiano Ronaldo could leave the club in the summer, but doubts it will be to Manchester United.

The English Premier League champions are reportedly looking at ways to bring in Ronaldo, who enjoyed so much success during his six-year stay with United, in the summer transfer window.

However, according to Calderon, who brought in Ronaldo from Manchester United, there are only three clubs that can afford to find the transfer fee and pay the wages for Ronaldo, and United are not one of them.

"Cristiano Ronaldo said he was sad at the beginning of the season," he told talkSPORT. "I think the relationship with the current president is not a good one, maybe because the president doesn't like the players he inherited.

"He did the same with Arjen Robben and Wesley Sneijder. It was unbelievable that when he came he decided to give them away.

"Ronaldo wanted to breach his contract. The truth is he didn't want to extend his contract and it's only got two years left. In the last few years it's a rule that you have to extend the contract or sell. If not, then the player is worth nothing.

"There are not many teams that could afford to pay him what he deserves and who can pay Real Madrid what they are asking for.

"There are three clubs -- Manchester City, PSG and Chelsea. I don't think any other club is going to pay that amount of money for a player."

Calderon, though, does expect Real Madrid to make an announcement over a deal with Ronaldo, with both parties reportedly finding ways to work out a new contract.

"They (Real) are going to negotiate the contract now and they will make a decision," Calderon added. "It's something we will know in a few weeks.

"The president doesn't need to keep Cristiano Ronaldo to be re-elected because no-one else is in the running.

"In a different world he would have agreed a deal (privately) to let him leave next summer, then said to the fans that he (Ronaldo) was going to extend his contract.

"Then they would have an agreement to leave the club when someone has the money."

United do have plenty of sponsorship money available, and a deal could be made if deemed necessary by new manager David Moyes.

Ronaldo has said of his intention to honor his contract with Real, but could be tempted to move back to Old Trafford, even with his mentor Sir Alex Ferguson retiring at the end of this season.