Former Athletico Paranaense player Pablo kisses the trophy after winning the 2018 Copa Sudamericana. NELSON ALMEIDA/AFP/Getty Images

There are few more explosive issues in Brazil than the thorny question of how many genuinely big clubs the country can count on. It is a subject where once the touch paper has been lit, it is advisable to retreat to a safe distance.

A leading local analyst of football finance was in the eye of the storm last week for arguing that, in truth, just four of Brazil's clubs are currently worthy of the title -- Flamengo of Rio plus the trio of Sao Paulo and their local rivals Palmeiras and Corinthians.

To the fury of fans of other traditional outfits, he declared plenty of others to be ex-big clubs, losing status as a consequence of financial limitations.

The conventional view is that Brazil has 12 traditional giants; the big four from Rio (Vasco, Fluminense and Botafogo as well as Flamengo), four from Sao Paulo state (Santos plus the three mentioned above), and two each from Belo Horizonte (Atletico Mineiro and Cruzeiro) and Porto Alegre (Gremio and Internacional). The leading clubs from the North East -- the likes of Bahia and Vitoria, Sport and Santa Cruz -- are often seen as potential giants, teams with mass support who have not been able to be consistently strong at national level.

If this is criteria to be considered "big," then 12 is now an underestimate. If, for example, Botafogo can claim big club status because of their glorious past, then Athletico Paranaense can make the same claim based on their powerful present and promising future.

Athletico are a club that think big. Over a decade ago, one club executive stated that they had the ambition of becoming the biggest football club of the Americas. This is setting the bar extraordinarily high -- unattainably high, surely, since their southern city of Curitiba has a population of under 2 million, and is at best the fifth footballing city of Brazil.

But they are trying to walk it like they talk it. Athletico are bold and forward looking. The club are always on the lookout for a fresh idea. Their first team, for example, takes no part in the State Championships that are staged in Brazil from the end of January to mid April. The club president dismisses these competitions as a waste of time.

A reserve squad gets game experience representing the club in the Parana State competition, while the first teamers are kept back for the important stuff. No other major Brazilian club has the courage to follow suit.

They won the Brazilian title in 2001, when it was staged on a play-off basis. The switch to a league format has clearly favoured the wealthier clubs from bigger cities. Athletico also reached the final of the Copa Libertadores in 2005, losing to Sao Paulo. There they were hampered by being unable to stage the home leg in Curitiba as their stadium did not have the required 40,000 capacity.

That is no longer a problem. The Arena da Baixada ground was inaugurated in 1999, but it was not fully completed until the works for the 2014 World Cup were carried out. Now housing over 42,000, it is a splendidly compact stadium -- where last week Athletico made all of South America sit up with the way that they brushed aside Argentine giants Boca Juniors on the way to a thumping 3-0 win.

Marco Ruben, right, wheels away to celebrate in Athletico Paranaense's 3-0 win over Boca Juniors. HEULER ANDREY/AFP/Getty Images

That was a huge night for the club. True, in December of last year they won the Copa Sudamericana, beating Junior of Colombia on a penalty shootout. But the Sudamericana comes nowhere near the Libertadores in terms of prestige, and over the two legs Junior had been by far the better side.

But Athletico took the confidence, took the prize money and moved on. With an eye on the finances they sold star centre-forward Pablo, who has scored both their goals in the Sudamericana final. To replace him they brought in more of a penalty area operator, the experienced Argentine Marco Ruben. Everything fell into place last Tuesday night, when the Boca defence were reduced to tatters and Ruben helped himself to a hat trick. Seeing off the six-time champions in such emphatic style sent out a powerful message: Athletico are genuine challengers.

They may come from outside the traditional centres of the Brazilian game, they might be taking part in the Libertadores for only the sixth time, but they are in it to win it.

And that is why this Tuesday's match is so important. Playing at home to Boca was the glamour game. Tolima of Colombia do not possess the same box office appeal, but they pose a threat. They have already beaten Athletico in Colombia. A repeat performance in Curitiba would almost certainly cause Athletico to drop from first in the group to third. In this case the Brazilians would be outside the qualification slots with two games to go -- and both of them are away from home in difficult venues (at altitude against Jorge Wilstermann of Bolivia followed by the final game away to Boca in the intimidating Bombonera stadium).

If Athletico Paranaense really want to be big, then, they will need to rise to the occasion once more, and take on Tolima with the same vigour that last week proved too much for Boca Juniors.