There's something slightly comical about the fact that Sunday's Copa América final will feature Uruguay and Paraguay. In the past two Copa finals, Brazil have met Argentina, and the organisers did everything in their power to ensure a repeat. Even with both underperforming there was almost no possibility of them meeting before the final, something they ensured by both going out in the quarter-final.

Whether the rise of the less-fancied nations represents the increasing strength in depth in South American football or the lessening quality of the Big Two (or, more likely, both) is a question only time can answer. What we have now is a final between two sides noted for their pragmatism who, between them, have a goal difference of plus three for the tournament. Never mind whether goals are overrated; this tournament has suggested that winning is hardly worth the effort.

It would be easy to be scathing about Paraguay, to mock them as bruisers and brawlers who play dreadful negative football. They have, after all, reached the final of the Copa América without winning a game, and have drawn three of their five matches 0-0. They've had players sent off in each of their past two games, and their semi-final win over Venezuela climaxed in a mass on-field punch-up.

At the World Cup they were a case study in tedium, the grinding last-16 win over Japan so dull that it was only the sense that it was such over-the-top dullness that it must be self-aware, almost ludic, like some piece of post-Le Corbusier brutalist architecture, that prevented the game challenging the Ukraine-Switzerland stalemate from 2006 as the worst game ever played in a World Cup knockout stage. So it would be easy to condemn them, and in many ways it would be justified.

But let's at least make a case for the defence. Paraguay is a country of 6.5 million people. It has no great natural resources. That it's qualified for the final stages of four successive World Cups is remarkable; that it's in the final of the Copa América after an absence of 32 years even more so. The modern era of its football was essentially shaped by Sergio Markarián, the Uruguayan who coached Peru at this tournament, when he was in charge of the national side in the early 90s. He imbued them with the characteristic Uruguayan virtues of toughness and organisation – an export that, 20 years later, could come back to haunt La Celeste on Sunday.

In the group stage Paraguay were far more expansive than they had been at the World Cup. That they drew 0-0 in their opener against Ecuador was mystifying (this is more generally true; the goals per game ratio of this Copa is dire – 1.92 – but that is not only down to defensive tactics; there have been an awful lot of chances missed, the woodwork seems to have taken a pounding and a number of goalkeepers have been inspired. Certainly this has felt far less negative than the Africa Cup of Nations in Mali in 2002, which yielded only 1.5 goals per game).

Paraguay then conceded in the last minute to draw 2-2 against Brazil and conceded two in the final two minutes to draw 3-3 with Venezuela.

Marcelo Estigarribia sparkled on the left wing. Roque Santa Cruz played as a second striker with composure and intelligence. And at the back of the midfield, the hunched, rotund figure of Néstor Ortigoza mixed crunching tackles with eye-of-the-needle passes. They were second-top scorer in the groups.

The concession of those late goals, though, has taken a toll. The coach, Gerardo Martino, removed Ortigoza for the quarter-final with Brazil and replaced him with the far more defensive Victor Cáceres. Against Venezuela in the semi-final, it was Estigarribia who missed out, Cristian Riveros moving to the left as Jonathan Santana shored up the midfield. In both knockout games they rode their luck: Brazil missed a preposterous number of chances; Venezuela hit the woodwork three times. But when it came to penalties, they were the side who held their nerve, and the excellent Justo Villar was the goalkeeper who saved the crucial kick (although given Brazil missed the target with three of the four they took, he hardly needed to).

Even Villar seems a little stunned by how it has gone. "It feels like a miracle," he said. "But after two lots of extra-time we arrive at the final with almost no oxygen, with five or six injured and one suspended. Uruguay is in a different state. Their key players are rested, but we will fight to the utmost."

The absence of Santa Cruz through injury has cost Paraguay creatively.

Although Nelson Haedo Valdez is a sympathetic figure – early in his career, he left home for a club 200km away, initially sleeping under a stand until he started collecting pay cheques – he lacks finesse. It hasn't helped, either, that both first-choice left-backs were injured for the Venezuela game, leading Martino to select Ivan Piris, more naturally a right-back, on the left, which in turn presumably contributed to his decision to play a more defensive player in front of him.

So they have been negative, but there are reasons. Under duress it's only natural that they should return to the familiar safety-first industry that has served them so well over the past two decades. That might not be to everybody's taste, but it's reassuring to know it's there, that in an era in which international football is decreasing in importance, there is still a nation so determined to succeed at it that it will risk opprobrium for the way it goes about attempting to prosper in it. Paraguay's football may be brutalist, but football itself would be duller if everybody played the same way.

Difference, almost in itself is a good thing: there were campaigns, even, to save the Trinity Square car park in Gateshead when the bulldozers moved in last year. Paraguay, following the principles of Markarian – Le Corbusier dressed as Sergeant Bilko – are football's equivalent. Ugly, but effective and ultimately strangely admirable, if only for the two fingers they have waved in the face of the marketers by failing to lose to Brazil.