Cristiano Ronaldo 'reduced to tears' by Sir Alex Ferguson during star's early days in ruthless Manchester United dressing room

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Cristiano Ronaldo broke down crying in the Manchester United dressing room early in his career after struggling to cope with Sir Alex Ferguson's harsh treatment, a new biography has revealed.

Ronaldo, now at Real Madrid and considered one of the two best players in the world, has long credited Ferguson's legendary methods in helping him to the top during their time together at Old Trafford.

And it seems the former Manchester United manager sought to get the best out of his greatest-ever talent by emotionally testing him in the unforgiving and relentless dressing-room environment that existed during his time in charge.

Cristiano Ronaldo is said to have cried after a Manchester United dressing down from Sir Alex Ferguson

Ferguson helped nurture Ronaldo after signing him in 2003 and developing him into the world's best player

Ronaldo is now seen as one of the top two talents of a generation, having benefited from Ferguson's treatment

Ferguson recognises Ronaldo as one of just four 'world-class' talents that he had at his disposal in his 27-year trophy-laden reign at United - Eric Cantona, Ryan Giggs and Paul Scholes were the other three - but clearly felt that the Portuguese forward needed reminding of his responsibilities at times.

The Scottish boss signed Ronaldo as an 18-year-old and in his first season, after a poor showing back in his homeland against Benfica, Ferguson is said to have torn into his young talent.

Guillem Balague's book, published in the Telegraph, reads: 'In the dressing room, Ferguson could not contain himself: "Who do you think you are? Trying to play by yourself? You’ll never be a player if you do this!"

'Ronaldo began to cry. The other players left him be. "He needed to learn," said (Rio) Ferdinand. "That was a message from the team, not just from Ferguson: everyone thought he needed to learn".'

Ferguson's treatment began to bring the best out of Ronaldo in training and increasingly with the first team in matches.

The dressing room criticism for Ronaldo came after a poor performance against Benfica back in Portugal

Ferguson would take time to explain to Ronaldo why he had criticised him in front of the rest of United's squad

Established players including Ferdinand and Quinton Fortune would reportedly remind him of his tears in Lisbon with comments such as: 'He’s crying in the changing room again!', 'F***- off! What are you talking about?' and 'Cry-baby, cry-baby!'.

Ronaldo labelled Ferguson as a 'father figure' in a BBC documentary looking back over the Scot's career last month, but in the early days at Old Trafford that was as much a jibe at the player as a compliment to the manager.

Ferguson would treat Ronaldo differently to other players, criticising him in front of team-mates but giving him time to explain his reasoning to develop the world's best up-and-coming talent.

Ferguson labelled Ronaldo as one of only four world-class talents he ever had in his possession at United

Fellow players including Rio Ferdinand would joke that Ronaldo was United manager Ferguson's son

Balague's book, CRISTIANO RONALDO: The Biography by Guillem Balague, to be released on November 5, says: 'Ferguson had never treated any other player with the same respect and affection as he did Ronaldo. The squad would make jokes about the special relationship with a mixture of laughter and envy: "He’s your dad; he’s your dad!".'

Ronaldo went on to make 292 appearances for United, scoring 118 goals across a six-year spell which saw him winning the Barclays Premier League three times, the Champions League, one FA Cup and two League Cups before his £80million move to Madrid.