A superstar from the age of 17, Ronaldo spent the four years before the 1998 World Cup lighting up every football pitch he set foot on.
The teenager, who was a non-playing part of Brazil's victorious squad at the World Cup on American soil in 1994, joined PSV Eindhoven in the Netherlands after the tournament on the advice of international colleague and former PSV striker Romario.
He'd previously emerged at Cruzeiro in his native Brazil as a 16-year-old, scoring 44 times in 47 senior appearances. Such was his talent, the goals continued to flow in Europe in PSV colours, with 35 in 36 games in all competitions in 1994/95.
A knee injury limited Ronaldo the following season, but he still scored 19 times. Then came a move to Barcelona for a world record of £13.2m and arguably the best individual season of his club career. After 47 goals, a Copa del Rey title and the UEFA Cup Winners' Cup, Internazionale put forward another world record bid, taking Ronaldo to Italy for £19.5m in 1997.
He continued to thrive in Serie A, a league notorious for overly defensive tactics. It meant that by the time of the 1998 World Cup in France, there was one name on the lips of fans around the globe: Ronaldo, O Fenômeno - the phenomenon.
It was his tournament, and no one was surprised when Brazil reached the final. Ronaldo had scored four goals en-route, including one in the semi-final against the Netherlands. He was supposed to then inspire Brazil to victory against the hosts, bringing the Selecao a second consecutive title.
He was only 21 years of age, but the hopes of an entire football mad nation, as well as the attention of the wider world, fell on his young shoulders. Then, in one of the most controversial moments in World Cup history, Ronaldo's world fell apart and the conspiracy theories began.
The superstar was mysteriously left off Brazil's team sheet when it was submitted just over an hour before kickoff, a shock omission that resulted in anyone and everyone coming up with their own theory as to what could possibly have happened.
There was talk of some kind of dispute within the Brazilian squad as the team had oddly failed to emerge for the pre-match warm-up. Ronaldo was said to be nursing an ankle injury, then a stomach bug. His knee was supposedly troubling him and there were questions about his weight. Had he been deliberately poisoned? Some went as far as asking.
Yet a revised team sheet was soon submitted around half an hour later. Having been replaced by Edmundo in the original, Ronaldo's name was now back on it and the 'mayhem' that had been caused by his earlier omission could subside, though the questions did not stop.
It became apparent only after the final that Ronaldo had suffered a convulsive fit in the hours that led up to the game. Coach Mario Zagallo made the decision around four hours before kickoff that 'R9', the player the planet desperately wanted to see, would not play. Yet Ronaldo is said to have pleaded with the three-time World Cup winner that he was fine.
On the field, Ronaldo was clearly not fine. He was nothing more than a shadow of his usual self, simply going through the motions as France cruised to a 3-0 win to lift their first World Cup.
Ronaldo should have never played in his condition, but nobody was seemingly prepared to intervene. Team doctor Lídio Toledo told the commission that followed the tournament: "Imagine if I stopped him playing and Brazil lost. At that moment I'd have to go and live on the North Pole."
One of the more popular conspiracy theories is that Nike stepped in and made Ronaldo play against medical advice. The sportswear giant had invested more than £100m in Ronaldo and the Brazilian team, creating an incredible branding campaign. Could they afford to have their superstar not appear on world football's greatest stage when it mattered most?
Despite no evidence to support it, many believed the Nike conspiracy to be true. The company has unsurprisingly always strongly denied any such interference and nothing was ever proven. Ronaldo himself declared in 2001, "the only thing Nike have asked of me is that I wear their boots."
Only a handful of people know the real truth about what happened to Ronaldo on the day of the 1998 World Cup final, but it will always remain one of football's most popular conspiracy stories.
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