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Cristiano Ronaldo: Subject of interest.

The build-up to Tuesday's Champions League quarter-final clash with Porto was dominated by fresh reports of a move to the Spanish capital - something Ferguson branded "pathetic".

It followed last summer's ugly and protracted attempts by Real to talk up a transfer for the 24-year-old, who has since been crowned world and European player of the year.

Ronaldo caused controversy at the time, meanwhile, by revealing he dreamed of one day plying his trade at the Bernabeu.

In an interview with CNN, Ferguson admits he has sometimes struggled to prevent Ronaldo's head from being turned.

"I think that he's had temptations and I think there have been periods when you've seen the effect of it (on the pitch)," the Scot said. "He's lucky in the sense that people here can tell him the truth and be straight with him and he appreciates that, and he has responded to that."

Ferguson praised Ronaldo for having the strength of character to know when he had overstepped the line in his tentative courting of Real.

"If it stays with him and changes him as a person then you have a problem," he said. "Fortunately Ronaldo has good human qualities. He's a good guy.

"He knows when he's gone too far and he draws back in after that."