Cristiano Ronaldo has the mental age of a 12-year-old, according to former Manchester United team-mate Mads Timm, though he believes the Real Madrid star benefits from his selfishness.

Timm spent six years at Old Trafford from 2000, but made just one first-team appearance, coming on against Maccabi Haifa in the Champions League and had loan spells at Viking, Lyn and Walsall before his departure.

The Dane may not have had a prosperous spell at United, but he remembers sharing a dressing room with Ronaldo and pointed out the Portugual international's self-centred mentality.

"He's completely indifferent to the collective side of the game," Timm wrote in his biography Red Devil. "It was 'me, me, me'. Today, after so much success, he can still get annoyed when one of his team mates scored instead of him.

"Mentally, he reminds me of when I was a 12-year-old. I think he doesn't care what people think of him and that's one of the reasons why he has been able to survive in professional football."

But Timm, 31, was in awe of Ronaldo's confidence and said he struggled whenever he came up against the three-time Ballon d'Or winner in training.

"Cristiano Ronaldo was the complete opposite to me. I hated the atmosphere in Manchester," he said.

"He was totally the opposite. He was focused and he had unwavering faith in himself and that was reflected out on the pitch.

"I remember a practice match in training when I was the left wing and he was on the right on the opposing team. Every time we crossed, he'd just fly past me. I was hardly ever out of breath after a training session... but that day, he left me gasping."