Suddenly, there are no certainties. The relegation of River Plate last Sunday, an event that seemed impossible and yet in hindsight looks inevitable – a slow motion slither of nine games without a win at the end of the season as the cliff edge got closer and closer – has had a profound effect on the mood of Argentinian football. If something as seismic as River being relegated can happen, who knows what the Copa América, which begins on Friday, might bring.

For the hosts, there is great opportunity, but with that comes great pressure, and it is the sense of expectation that is exercising commentators in the week leading up to the tournament. River's collapse showed what an albatross expectation can be. As the columnist Andrés Prestileo wrote in La Nación this week, "the Copa has become treacherous: a win would bring to Argentina a gratification less intense than the frustration were they to lose." Little wonder Sergio Batista, the tough-tackling bearded anchor of Argentina's 1986 World Cup winners who replaced Diego Maradona as national coach after the World Cup, has spent much of the buildup talking about the need for "patience" and insisting the priority is fashioning a side for the 2014 World Cup in Brazil.

If they do win on home soil, Argentina will go back ahead of Uruguay as the most successful side in Copa América history, but Argentina have not won a major tournament since 1993, and have not beaten anybody apart from Mexico in the knockout stage of the World Cup since 1990 (not including penalties). The shambles of the World Cup, when Maradona's team was hammered in the quarter-final by Germany was just the continuation of two decades of underachievement; at the moment particularly, there is a tremendous fear of talent being wasted. If you have a player like Lionel Messi, you really need to make the most of him, especially when he is backed up by players as gifted as Carlos Tevez and Sergio Agüero, players most nations would happily build a team around.

Batista led Argentina to Olympic gold three years ago, and has brought with him a welcome sense of authority, but it remains to be seen how long that lasts amid the fervour of a home tournament. Initially it seemed he had decided you can have too much of a good thing and looked likely to start against Bolivia in La Plata on Friday with Messi as a false nine flanked by Angel Di María and Ezequiel Lavezzi. Reports from training, though, suggest Tevez could yet get the nod ahead of Di María on the right. Esteban Cambiasso and Javier Zanetti have been recalled from their exile, and the midfield three of Javier Mascherano, Cambiasso and Ever Banega looks far better balanced than anything in Maradona's reign.

A comfortable win over Bolivia would help Argentina erase the shame of their most embarrassing moment under Maradona – the 6-1 World Cup qualifying defeat at altitude in La Paz – but anything else would lead to clamours for change, with Lavezzi and Di María the most vulnerable. It remains to be seen what effect River's relegation will have on the atmosphere; will the sense of grief – and in context that's not too strong a word – felt by a vast swath of the nation's fans make them more desperate for compensatory success with the national team, or will it just leave them numb?

In that regard, it's probably no bad thing the tournament, unlike previous Copas in Argentina, is being taken around the country, away from the crucible of Buenos Aires to Jujuy and Salta in the north, Mendoza and San Juan in the west and Córdoba and Santa Fe in the central belt. The final will be held at the Monumental, the scene of rioting after River's relegation play-off defeat to Belgrano de Córdoba on Sunday and venue of the 1978 World Cup final, but before that the closest the tournament gets to the capital is La Plata.

The horror prospect for Argentina is not merely that they don't win, but that Brazil do, lifting the Copa for the fifth time in six attempts. (The possibility of them beating Argentina in the final is almost too horrifying for the hosts to contemplate; if that did happen in the first game at the Monumental after River's relegation, there would have to be some sort of exorcism before the stadium could be used again).

The economics of the past decade mean that it has now become common for Argentina players to be sold to the Brazilian league, something almost unthinkable in the 90s, while Brazilian teams have a definite edge in the Copa Libertadores – 14 quarter-finalists in the past five years to Argentina's six. To have that superiority rubbed in their faces on home turf would be unthinkable.

After the pragmatism of the Dunga years, this is a Brazil team still adapting to the more liberal outlook of Mano Menezes. The system is the classic 4-2-2-2-cum-4-2-3-1 that Dunga employed, with Pato as the main central striker and Neymar to his left; the Santos duo of Ganso and Elano take the attacking midfield berths with one pulling right, and with Lucas Leiva holding in front of the back four and Ramires shuttling. The formation may be the same as Dunga's, but the style is much more fluid and attacking.

Argentina and Brazil are clear favourites, but Uruguay showed at the World Cup how dangerous they can be. Oscar Washington Tabárez likes to tinker tactically, but his side will essentially look to keep things tight and rely on the fluent and versatile attacking trident of Diego Forlán, Edinson Cavani and Luis Suárez for goals. Their group, Group C, initially looked the hardest to call, but while Chile, still adapting to life under Claudio Borghi after Marcelo Bielsa's resignation are a clear threat, Peru and Mexico have been beset by problems.

Having played in the Gold Cup, Mexico, who beat USA in the final last Sunday, sent only an Under-22 side bolstered with five overage players but whatever chance they had was severely undermined when eight players were sent home earlier this week for allegedly consorting the prostitutes. Peru, meanwhile, having finished bottom of Conmebol World Cup qualifying have lost Claudio Pizarro to a thigh strain while Juan Manuel Vargas and Jefferson Farfán have had injury-hit buildups.

With the two best third-place sides making it through to the quarter-finals along with the top two in each group, there's a sense that the early stages are as much about jockeying for position and finding form as they are about the practical business of qualification. Nobody doubts Argentina will make it through, but dropped points in their second game against a Colombia side featuring the Porto duo of Radamel Falcao and Fredy Guarín could leave an awkward quarter-final against the second side from the Uruguay group rather than a third-placed team. Had Japan been there, as was planned, in fact, Group A might have been challenging. They withdrew following the earthquake and consequent delays to the J-league season, though, and a Costa Rica Under-22 side with five overage players looks a significantly less daunting prospect.

Paraguay, World Cup quarter-finalists, provide the main threat to Brazil in Group B. Gerardo Martino remains as coach, which means the obdurate 4-3-2-1 should endure, fronted by Lucas Barrios, a key figure as Borussia Dortmund won the Bundesliga title last season. Ecuador have Antonio Valencia on the right and a front two with Premier League experience in Cristian Benítez and Felipe Caicedo, but are some way short of the side that qualified for the 2002 and 2006 World Cups, while Venezuela, although they are improving and reached the quarter-finals on home soil last time round, are still minnows.

Teams can develop momentum over the short span of a tournament, individuals can hit an unprecedented patch of form (the Schillaci-Babb principle), but to start with, the narrative of this tournament looks like being about Argentinian self-assertion, about stopping Brazil, and about making sure this richly gifted generation delivers on its potential.