With nine minutes of extra time remaining in the 2011 Under 20 World Cup final in Bogota, and Brazil drawing 2-2 with Portugal, Oscar picked up the ball wide on the right.
A jink of the shoulder created a fraction of space and he clipped the ball over Mika, the Portugal goalkeeper, and inside the far post. It was his third goal of the game and proved to be the winner. But the question everybody was asking was, did he mean it?
A little over a year later, as Oscar made his first start for Chelsea, against Juventus in the Uefa Champions League, people were asking the same question. He had already scored once with a deflected shot when, toward the end of the first half, the ball was played to him by Ashley Cole.
He had two men tight behind him, but where others might have looked for a free kick or sought to hold the ball up, he back-heeled the ball to one side of the approaching Andrea Pirlo, ran around the other, and on the turn, whipped a dipping, curling shot into the top corner.
Did he mean it? It was so unexpected, such an unusual movement, that the immediate assumption was that he had not - but nobody, surely, could have reacted that quickly to a miskick.
Perhaps Oscar did get lucky on one, or both, occasions, although he insists not. Certainly in Bogota, there was a strange sense of the pitch opening itself up for a shot of the nature he attempted fractionally before he attempted it, and if that is the case, it speaks of an extraordinary capacity on Oscar's part to visualise the field.
It is one thing to see the possibility sitting in a press box high up in the grandstand, quite another to see it amid the chaos on the pitch - and of course, something else again to have the technical skill to pull it off.
This, surely, is an example of what the US evolutionary biologist Stephen Jay Gould described as "the universality of excellence".
"I don't deny the differences in style and substance between athletic and conventional scholarly performance," he wrote, "but we surely err in regarding sports as a domain of brutish intuition ... The greatest athletes cannot succeed by bodily gifts alone ...
"One of the most intriguing, and undeniable, properties of great athletic performance lies in the impossibility of regulating certain central skills by overt mental deliberation: the required action simply doesn't grant sufficient time for the sequential processing of conscious decisions."
All players, of course, have that to an extent, but Oscar seems to have it to an extreme degree so that he can visualise what others cannot, so that he can see the possibility of goals and passes when others would see just a mass of bodies.
What he also has is a profound mental strength that has allowed him to move on from a scandalous transfer wrangle triggered when he walked out on Sao Paolo to join Internacional last season, claiming he had not been paid for several months.
It has also allowed him to adapt far more quickly than could reasonably be expected to the Premier League. There are few players who look at home in the rough and tumble of English football, fewer yet who do so a matter of months after leaving the Brazilian league, where skilful players are cosseted.
Yet there has been no need to ease him in gently: Oscar, 21, has started 39 games this season and come off the bench on 20 other occasions.
The goal he scored against Swansea City two Sundays ago was his 11th this season, but it was the one before that, a near-post header against Liverpool reminiscent of Didier Drogba's goal in the Uefa Champions League final last year, that confirmed his comfort in the English game.
Not only that, but he works hard and is disciplined enough to track: Roberto Di Matteo described his performance against Pirlo in that Juventus game as "tactically perfect".
As such, he represents the very best of modern breed of playmaker: tenacious as well as creative. But what makes Oscar truly special, as Tottenham Hotspur may find out tonight, is his capacity to conceptualise and execute passes that others do not see until they have happened.
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