Cristiano Ronaldo knows he is in the best form of his life, and he knows that such a period may not last for long. He only has to look at the fall from grace of Ronaldinho, the world’s best player two years ago, to appreciate how fleeting greatness can be. That is why, as he approaches the third international tournament of his career, he is already thinking about his legacy. “I want to leave my mark on football, on football history,” he said. “If I keep doing things as I am, if I stay humble and keep working hard, I think one day I’ll do it.” That day might come on June 29 at Vienna’s Ernst-Happel Stadium, in the Euro 2008 final.

Ronaldo has shown he has the taste, and the temperament, for international football. As Portugal coach Luiz Felipe Scolari put it, “I knew two stars with the same name, Ronaldo and Ronaldinho, from my work with the Brazil team, and I always hoped that Cristiano would be as good, or would become as good. I think that day has almost come.”

And while Manchester United, particularly in the last two trophy-winning seasons, have been the main beneficiaries of Ronaldo’s rise to prominence, this summer it is the turn of Portugal. “I play with a passion in the national team because it’s my country,” he explained recently. “The ambition remains the same, to help the national achieve trophies.”

Despite giving the world players like Eusebio and Luis Figo, Portugal are yet to win a major tournament, though the country is united in its belief their hoodoo can finally be lifted. That is because of Ronaldo, and specifically his relationship with Scolari, the Brazilian who has been a mentor to him ever since his father Jose Dinis Aveiro died in 2005.

Scolari’s clever honing of Ronaldo’s talent in international football began at Euro 2004 when, as a 19-year-old, Ronaldo came off the bench to score with a powerful header in the opening game. Unfortunately, by then he had also conceded a penalty and Portugal ended up losing to Greece.

Scolari resisted calls to start Ronaldo for the next game, a must-win clash against Russia. Instead, he again came off the bench and set up Rui Costa for the second goal in a 2-0 win. He started the next game, a 1-0 win over Spain, and scored a penalty in the quarter-final shoot-out win over England. In the semi-final against Holland, he scored one, set up another and was voted Man of the Match. Portugal, the hosts, were in the final and the country had gone Ronaldo-crazy. But the final was a game too far for the expectant nation and outsiders Greece soaked up the pressure, scored from a set-piece, and shocked the continent. Ronaldo, who missed a late chance to level the scores, could not contain his emotions on the final whistle.

“We were in the final, and after all that had happened, all the hype in the country, it was wonderful to be part of it all,” he said. “But these experiences mark your life: losing a final with so many people watching, with the country hoping we would win… I was very sad, and I admit I cried.”

The tears did not surprise his mother, Dolores Aveiro. “He used to get upset very easily,” she remembered. “He used to cry when he’d pass the ball and his team-mate didn’t score. People started to give him nicknames. They called him ‘crybaby’ and ‘little bee’ because no-one could catch him.”

Ronaldo changed as a person and a player over the next two years, as two key events shaped his character development. First, in September 2005, before a World Cup qualifier against Russia, Scolari told Ronaldo that his father had died. “The death of his father reminded me of the death of my own father,” said the Brazilian.

“We talked for a while and Ronaldo, while obviously not at peace with what had happened, was able to calm down a little bit. He was more relaxed. We shared the same grief and because of that, we also shared what happened next. I asked him whether he wanted to play or not [against Russia] and he decided to stay with us. These are moments football can give us: when it can be a positive. There can be difficult times followed by unforgettable moments, which are often from decisions like he made.”

The game ended in a goalless draw but more significant than that was the new bond that had formed between Scolari and Ronaldo. That conversation, and the subsequent decision, marked a new era in their relationship: the pair would now be bound by trust, loyalty and mutual respect. “It isn’t natural to lose your father at 20 and you learn things about yourself,” Ronaldo said, “You have to be strong and I changed a lot over the next two years.”

He did so without ever forgetting his father. “Unfortunately he’s not physically with me anymore, but I can feel him always close to me. I have many memories from him because he was very important to my development as a player, as a person, as a man. He was one of those responsible for what I am today.

“Every day he gave me motivation. When someone was flattering me, he couldn’t say a word, he was so enthusiastic and proud. But nobody would dare to do make any criticisms of me: he would argue my case!”

Ronaldo has claimed United coach Sir Alex Ferguson has since become a father-figure (he once said, “sometimes he shouts at me like a father but it is always to improve me”) but back home, Scolari was monitoring his development with interest. “I watched that young kid grow up over the past five years,” the Brazilian said.

The World Cup was the moment Ronaldo showed his two greatest attributes – his skill and his courage – on the biggest stage of all. He was the bright spot in Portugal’s three group wins, before his creativity so frightened Holland that he was kicked off the pitch in one of the most violent games in World Cup history. Then came another quarter-final against England, and this time Ronaldo was the hero: scoring the winning penalty in the shoot-out (although he was seen as the scapegoat for England’s failure after being caught winking on camera following the sending-off of Wayne Rooney).

“The World Cup changed me,” said Ronaldo. “I got through everything in Germany, good and bad moments. People only remember the Rooney thing, but I had a good tournament. Against England, for example, I took the decisive penalty during the shoot-out, but nobody remembers that.”

He is not quite right: The Times’ Chief Sports Correspondent, Matt Dickinson, defending Ronaldo against claims he is not a big-game player, pointed to his performances in both Euro 2004 and the World Cup. “Just by scoring the penalty that sent England home from Germany, Ronaldo showed more nerve than any of our brittle millionaires,” he wrote.

“Scolari asked me if I wanted to take the last penalty, and I said, ‘Of course,’ even though I knew there was a lot of pressure,” Ronaldo continued. “If I had missed the penalty, people in Portugal would have hated me. By scoring, I was going to be the enemy of England. But I was playing for my country, and I didn’t think about the consequences. I am never afraid when I play football. I believe in myself and I try. Sometimes I miss, but you have to keep that confidence in yourself.”

Ronaldo returned to United as English football’s public enemy one but his performances soon silenced his critics. He ended the 2006-07 season as the Premier League’s top scorer and became the first player since Andy Gray in 1977 to win Young Player and Player of the Year awards.

Scolari was impressed and in February 2007, following the international retirements of Luis Figo, Costinha and Pedro Pauleta, handed the captain’s armband to Ronaldo for the friendly against Brazil in London. The game was on Ronaldo’s 22nd birthday, and Portugal won 2-0.

“He just doesn’t stop, no matter how much you demand of him,” explained Scolari. “Sometimes when we ask him to go easy, to avoid injuries for example, he wants to work even harder. If you set him a task, he wants more. That’s what I like about him: that and how he treats people.”

Scolari had not decided if Ronaldo should keep the armband going into Euro 2008. Nuno Gomes has also been the captain but as his place in the side is not certain, nor is his captaincy.

Scolari said he was going to commission Regina Brandao, a Brazilian psychologist, to analyse all the players and make individual reports on each player, from which Scolari will choose his ultimate leader.

“In the national team I’m proud to be one of the team captains,” Ronaldo said. “When Nuno plays, he’s the captain; if he doesn’t play, I am the captain. It’s a privilege to be the captain of my national team. It’s the same responsibility, because it’s not an armband that will change my way of playing. Things will be the same, regardless of whether I have the armband or not.”

And yet not everyone is comfortable with the progression of Ronaldo’s career. Porto forward Lisandro Lopez recently complained that Ronaldo-mania had gone over the top when he said, “I can even see Ronaldo in the soup here.”

“It’s a sign that people admire my work, my professionalism,” Ronaldo responded. “I’m Portuguese and people always speak about me. It’s a big level of responsibility, but I will try not to disappoint people.”

There are other fears in the Portugal camp: that the team is too reliant on Ronaldo; that Ronaldo tries to do too much on his own; and that Ronaldo in a Portugal shirt is a different player to Ronaldo in a Manchester United shirt. The player has heard them all before. “I want to play in the Euro like I have done in Premier League,” he said.

“I will focus myself on the national team and I will be ready for the Euro. The critics can ask more of me, but I don’t agree with that. I was the top scorer of Portugal in the last two qualifying stages and I’ve also had the most assists. I’ve shown in my club and in the national team that I’ve developed as a player and as a person. I’m ready for the big challenges.”

Four years ago, Ronaldo started the competition as a substitute: now he will be leading out the Portugal team with the expectations of a nation on his shoulders.

“Cristiano is an example of a ‘boy’ who has matured quickly, as a player and as a leader,” is how Scolari put it. “I think he is the best in the world: as a person, as an athlete, and as a member of the national squad.”