Just over two years ago, in February 2012, Argentina played a friendly away to Switzerland -- Tuesday's opponents in the World Cup second-round match -- and won 3-1. Lionel Messi scored all the goals, but did not claim all the glory single-handed. The standout feature of the game was the way Messi combined with Sergio Aguero; the two of them exchanged passes at dazzling speed and imaginative angles, and the Swiss defence could not lay a glove on them.
Rewind back to June 2005 at the FIFA World Youth Championship in the Netherlands: Messi and Aguero were roommates, and struck up a firm friendship. Their off-field relationship was already evident on the pitch as Argentina won the title. In Brazil, in Argentina's Belo Horizonte base, they have been sharing a room once more.
This time, though, they have been unable to combine to such good effect. Messi has risen to the challenge of the competition which will surely stand as his definitive statement as an international footballer. Aguero, though, has had a frustrating time. The stocky little striker has had an injury-plagued past few months at Manchester City -- and the impression that he is still some way short of full fitness was confirmed when he limped off with a muscular problem in the first half of Wednesday's match against Nigeria.
Initial worries that he might be out of the tournament have, it appears, proved exaggerated. He is back in training and might be fit enough to return for the quarterfinal Saturday -- providing, of course, Argentina get past Switzerland. This, though, is a challenge that they will have to overcome without him -- and very probably, with Ezequiel Lavezzi. Other options exist: Ricardo Alvarez could come in to play on the right of midfield in a 4-4-2, but the bolder move, the one befitting a team seeking to impose itself on the game, would be the introduction of Lavezzi, who replaced Aguero against the Nigerians.
There is an irony here. Lavezzi was also part of that Argentina under-20 process in 2005. He played in the qualifying tournament in Colombia -- when Messi made his big breakthrough. But a few months later Lavezzi was left out of the squad that went to the Netherlands for the FIFA World Youth Championship -- he lost his place to the younger Aguero, who had been making a big name for himself as a wonderkid in the domestic championship. And now Lavezzi stands by to step in for Aguero against the Swiss.
In this switch Argentina lose a magnificently talented penalty-area predator, one capable of tearing defences apart in the tiny spaces of the opposing penalty area. But they gain a natural winger, which may, in the collective context of the team, prove very interesting.
The 4-3-3 of coach Alejandro Sabella can leave the side looking narrow. Messi has been playing behind two strikers -- Aguero and Gonzalo Higuain, both thrown wide to open up space for Messi, but both looking to cut inside. They have made progress down the left flank, with Angel di Maria combining with full back Marcos Rojo. Down the right, though, there has been little threat, a deficiency Sabella has acknowledged. Against opponents with a cautious game plan, this lack of width has been a problem. Lavezzi could be the solution.
The Paris Saint-Germain striker is also happy to track back and mark the forward runs of the opposing fullback -- and Sabella has long been concerned about the vulnerability of his defence to quick breaks down the flanks. The chance has come, then, for Lavezzi to play himself into the first choice side, even if Aguero does make a swift recovery. Perhaps from the quarterfinals onwards, Sabella might be tempted to play Lavezzi and either Aguero or Higuain, who has looked sluggish so far in the tournament.
All this, of course, depends on beating the Swiss -- which could, in part, depend on the effectiveness of Ezequiel Lavezzi as a supplier of pace and width down the right.
Tim Vickery is an English journalist who has been based in Brazil for the past 20 years. He is the South American football correspondent for the BBC Sport.