So it is down to the big two as the South American Under-20 Championships moves towards Saturday's final round. Uruguay have qualified for this year's U-20 World Cup, scheduled for South Korea at the end of May. Hosts Ecuador and Venezuela are virtually assured of joining them, leaving one slot available for either Brazil or Argentina.
That is the consequence of Wednesday's 2-2 draw between the old rivals. It must have been one of the poorest games played at any level between these continent's traditional giants. Having displayed plenty of disjointed football throughout the tournament, Brazil and Argentina struggled to put three passes together.
But what the game lacked in quality, it gained in drama.
By virtue of a hotly disputed penalty, Brazil led 2-1 deep into stoppage time. At that point they had qualified and Argentina were out. Brazil did everything to run the clock down; their goalkeeper, a spectator for most of the game, went down with cramp to eat up a few more seconds. But in the 95th minute Brazil were punished for sitting too deep, Argentina managed to mount a coherent attack and a cross from the left was headed back across goal and inside the post by centre forward Lautaro Martinez.
Argentina, then, live to fight again. And fight they will, this time against Venezuela in Saturday's first game.
The Venezuelans have been the success story of the tournament. Defending well has allowed them to pick up confidence during the course of the competition. In eight games, the only defeat they've suffered was Sunday's controversial 1-0 loss to Brazil, losing to a late goal where a clear foul was committed before Felipe Vizeu lashed home. The Venezuelans bounced back with a very impressive 3-0 win over top of the table Uruguay, sealing their place in South Korea.
Argentina's best hope against a team that's conceded just five goals in eight games is that the Venezuelans might have overdone the celebrations and lost their focus in the build-up to their final fixture. Argentina could even get themselves ahead of Venezuela in the table but it would take a five goal victory.
Can a labouring Argentina side force Venezuela to concede as many goals in 90 minutes as they have let in during the preceding 720? Nothing is impossible in football but it would take an extraordinary Venezuelan collapse -- and a bad afternoon for Wuilker Farinez, the goalkeeper of the tournament -- for this to happen.
More realistically, Argentina will have to win and then hope that Brazil fail to beat Colombia in the next game. That also looks like a forlorn hope. The Colombians appear to have collapsed and it's possible to identity the exact moment it happened.
In the second round of the decisive phase they were drawing 1-1 with Argentina, coming back from the shock of conceding after 19 seconds to take charge of the game. They looked likely winners until, with 12 minutes to go, they lost midfielder Eduardo Atuesta to a very harsh straight red card. Argentina rallied, won the game in stoppage time and Colombia have subsequently slumped to a pair of 3-0 defeats. With no chance of qualification, they must surely be dreaming of going home.
The Brazil side do not lack talent. Their problem has been finding a collective notion of play. But against opponents who may well lack a little motivation, they should be able to win comfortably enough, booking their place in South Korea and almost certainly condemning Argentina to elimination.
The competition closes with the main event of the evening, Ecuador vs. Uruguay. This will probably be the match where the title is decided with Uruguay, two points ahead of their rivals, going into the match as favourites despite Wednesday's slip up.
But Venezuela are also in the hunt. If Ecuador and Uruguay draw, Venezuela will be champions providing they beat Argentina. They can also claim the title if Ecuador win, as long as they have beaten Argentina by a bigger margin.
The final round of the South American U-20 Championships will kick off with Venezuela having an outside chance of failing to qualify and a slightly better chance of ending up as champions. It's a fitting scenario for what has been an uneven tournament.