“Look mate, you’re going to need to sit in the front. If you sit back there it’s obvious I’m an Uber car and some taxi drivers could kick the shit out of me. It happened to someone I know about a week ago.” Such an overwrought arrival at EZE airport on 23 October was a strangely fitting prelude to two big, dramatic days of football in Buenos Aires. The semi-final draw for the Copa Libertadores – South America’s answer to the Champions League – had thrown up two huge games featuring four mammoth clubs and the tension was palpable across the city.

The rivalry between South America’s two greatest football nations is well established, thanks in no small part to their success in the Copa Libertadores. Argentinian clubs have won the competition 24 times, with Brazilian sides further back on 18, and they were about to go head-to-head in the semi-finals.

Well, not quite Argentina v Brazil. To be more precise, this was Buenos Aires v Brazil: the big two from Argentina’s capital city taking on a pair of giants from across the border. Two nights. Two games. One city.

First up, River Plate would welcome reigning champions Grêmio to El Monumental, their giant bowl of a home. The following evening Boca Juniors would cram close to 50,000 into the lopsided Bombonera – a ground one fan proudly told me looked like a collapsing cardboard box – for the visit of Palmeiras, the outright favourites to win the competition.

River Plate v Grêmio, Tuesday 24 October

River Plate fans squeeze into El Monumental for the home leg of their semi-final against Grêmio. Photograph: Alejandro Pagni/AFP/Getty Images

Things have not begun well in the central Buenos Aires neighbourhood of Palermo. With just a few hours to go until kick-off, I am still waiting for my highly coveted ticket. They sold out long ago and are rumoured to be exchanging on the black market for up to 10,000 pesos (£215). Tracking down someone willing to sell one has taken more than a dozen calls, a rudimentary grasp of Spanish and a large dose of faith.

Finally my ticket arrives and I’m off to El Monumental. Observed from up close, the largest stadium in Argentina is not unlike the Maracanã. It is vast and open, yet the sounds of the ground are not carried away on the wind – not on a night like this anyway. Overcoming reigning champions Grêmio – who beat Lanús, another team from Buenos Aires, home and away in last year’s final – would be a huge scalp for River and would also move the competition closer to a mouth-watering Superclásico final.

A River fanatic tells me tensions are always heightened when a Brazilian club comes to town and, sure enough, I see a gathering of police and fans outside one of the gates. A large number of fake tickets have been in circulation and some unlucky souls will not be able to pass through. To describe them as angry and frustrated would be a gross understatement.

Inside, Grêmio coach Renato Gaúcho is again disproving the idea that he lacks the tactical nous to deliver on the big occasion. Arthur was sold to Barcelona for £35m earlier this year and Grêmio are also without star forward Luan, but their holding midfielder Michel scores the only goal of the game and the Brazilian side leave Buenos Aires with a 1-0 lead, an away goal and the chance to wrap things up in the second leg the following week in Porto Alegre.

Boca Juniors v Palmeiras, La Bombonera, Wednesday 25 October

Boca Juniors fans at La Bombonera. Photograph: Alejandro Pagni/AFP/Getty Images

“Are you wearing socks?” It’s not the most traditional greeting I have ever received from someone who is giving me a ticket for a big football match, but I nod along. “Keep money and keys in your socks, then. I wouldn’t take a phone or anything you don’t really need. I never do.” It seems like sound advice to follow.

Palmeiras are the Brazilian side who most embody the sense of financial disparity in South American football. The side from São Paulo routinely outspend their rivals at home and abroad, offering relatively huge sums to the likes of goalkeeper Weverton, midfielder Lucas Lima and Colombian forward Miguel Borja. All are internationals and all have been signed to help Palmeiras land silverware.

The club’s latest bid for success also led to them dispensing with young manager Roger Machado midway through the season. They turned instead to the conservative pragmatism of Luiz Felipe Scolari, and the results have been positive so far. The 69-year-old took the job for the third time at the end of July and began his reign by overseeing 10 clean sheets in a row. The upturn in form took Palmeiras to the top of the table in Brazil as well as the final four of the Libertadores.

I approach the stadium 90 minutes before kick-off and the party is already in full swing. The layout of the “collapsed cardboard box” is comparable to Vasco da Gama’s stadium in the north of Rio de Janeiro, where small, densely packed streets make for a tremendous din. In the same way that a tightly packed stadium can produce a more vibrant atmosphere than a vast bowl of an arena, the tight roads and walkways in the neighbourhood of La Boca make it easier to soak up the atmosphere under the lights.

La Bombonera produces one of the most electrifying atmospheres in world football and Boca also possess one of the most instantly recognisable kits in the game. Yet the Brazilian football journalist Gilmar Ferreira tells me the club attract more animosity than River. “I really detest Boca,” he says. “They have the same image as Flamengo and Corinthians in Brazil. They try to play up this popular image they have away from the pitch.” Having lived in Rio for nine years, I can empathise with his point. Flamengo brand themselves garishly as a club of the people, yet their directors do not hesitate to charge ginormous ticket prices when they reach a final.

Back at La Bombonera, two well-struck goals from Darío Bendedetto have given Boca a deserved 2-0 lead from the first leg. It’s an excellent triumph over a richer opponent and yet another disappointment for a Brazilian club on the biggest stage. Given their financial advantages, Brazilian clubs should be dominating the Libertadores. Yet in the three editions of the tournament between Atlético Mineiro’s win in 2013 and Grêmio’s triumph last year, not one Brazilian club reached the final – a record rightly seen as scandalous by the nation’s sporting press.

Boca fan Marcelo Mesqueira puts the struggles of Brazilian sides down to a superiority complex. “There’s an arrogance about Brazil, from the press to the fans. They think they’re better than other countries and that feeling transfers itself to the players. Before the Grêmio v Lanús final last year, there were Brazilian journalists saying they didn’t know much about Lanús, and, because they didn’t know a lot, it would be simple for Grêmio. What kind of attitude is that for a professional to have?”

That feeling of defiance resonates around the ground and there is much glee from Boca fans when the final whistle confirms their defeat of a richer rival. The job, however, is only halfway done.

Boca Juniors celebrate their defeat over Palmeiras in the semi-finals. Photograph: Miguel Schincariol/AFP/Getty Images

The aftermath

A week later and both Argentinian teams have secured their places in the final. River Plate knocked out reigning champions Grêmio on away goals with a 2-1 win in Porto Alegre and then Boca completed their aggregate 4-2 win over Palmeiras in São Paulo to set up the final Buenos Aires wanted. This being South America, though, it wasn’t without controversy.

Grêmio appealed to Conmebol to kick River out of the competition after it emerged that their coach had defied a touchline ban in the second leg and entered the dressing room at half-time to speak to his players. Marcelo Gallardo admitted his guilt – “I broke a rule, I recognise and take responsibility, but it is what I needed and I don’t regret it” – but Grêmio’s complaints fell on death ears. Rather than annulling River’s victory, the confederation handed the manager a fine and a suspension.

The glitz and romance of that one-city final remains, yet there were still howls of derision from Brazil. Earlier in the competition, Santos were punished with a 3-0 defeat for fielding an ineligible player against Independiente, but when River fielded Bruno Zuculini – also ineligible – against Flamengo in the group stage they went unpunished. On the surface, the Libertadores has the final of its dreams – two giants from the same city making history in a grand Superclásico that the whole world will lap up. The means of reaching it, however, remain controversial.

• This is an article from The Set Pieces

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