Cristiano Ronaldo used to train alone behind a hill so his teammates wouldn't see him fail and make mistakes

• Cristiano Ronaldo used to train alone at Manchester United so his teammates wouldn't see his mistakes.
• "He used to go behind the hill and do his training on his own," said former coach Mick Clegg.
• Speaking in a documentary about the Portuguese star, Clegg also described him as "an absolute genius."

Cristiano Ronaldo used to hide behind a hill and train alone at Manchester United so that his teammates wouldn't see him make mistakes.

That's according to the club's former power development coach Mick Clegg, who described the Portuguese player as a "genius."

"The thing about Cristiano when he was at United, I know that he came to use United as an apprenticeship," Clegg said during a new BBC documentary about the five time Ballon d'Or winner, titled "Cristiano Ronaldo: Impossible to Ignore."

"At Carrington [United's training ground], there was a hill at the back, just away from the training ground, and he used to go behind the hill and do his training on his own.

"And I asked him about that one time, I he said, 'Well, you know, there is nobody there so I don't have to worry if I do a skill wrong or anything, I can practice it and nobody's watching me.'"

Ronaldo would practice skills on his own for a few days, Clegg said, before unleashing them on his teammates in training games.

"I remember watching him in matches and he'd make a mistake or he'd get caught, he'd fall down and he'd have the crowd shouting at him, players shouting at him.

"It didn't bother him. He didn't want to make mistakes of course, but then he would know: 'This is the bit I've got to work on', and he'd go on and work on it."

Ronaldo joined Manchester United from Sporting Lisbon in 2003 for a fee of $24 million, which, at the time, made him the world's most expensive ever teenager.

After an initial struggle, he soon adapted to the English game and went on to become one of the country's, and world's, best players.

In six seasons at Old Trafford, Ronaldo scored 118 goals, helping the club to win three Premier League titles, the FA Cup, two League Cups, and the Champions League.

He was awarded his first ever Ballon d'Or in 2008, before completing a world record $118 million move to Real Madrid in 2009.

"People said to me: 'How did you get that skinny kid into that big muscly guy in six months?'" said Clegg.

"There was never any skinny guy anyway, he had a great physique when he first came. But it took five-and-a-half years that we worked together for him to produce what he wanted to produce."

He added: "There is no magic pills on a journey like Cristiano Ronaldo's. It's all about hard work, day-in, day-out, week-in, week-out, year-in, year-out.

"He's an absolute genius. An absolute genius."