Hosting the World Cup was a tragedy for Brazil in 1950 and a farce in 2014. But there is one fortress that has yet to fall. They have never lost a World Cup qualifier at home -- though this has never seemed more likely than Tuesday night when world champions Argentina pay a visit to Rio de Janeiro's Maracanã stadium.

After five rounds of the 2026 qualifying campaign, Argentina are top of the table. Brazil are down in fifth, and if Ecuador had not been punished for administrative irregularities, they would be sixth. After four bad games in a row -- and an unprecedented two consecutive defeats in qualification, some are suggesting that this is the worst Brazil side in memory. And this leads to the heart of the matter -- Argentina look like a team, Brazil look like a shambles.

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The Selecao's coach Fernando Diniz has run into predictable difficulties. He has built a career around being unorthodox. He trusts his players to construct relationships that will lead to flowing off-the-cuff passing movements. But this needs time to implement, and lack of time to train is the bane of the national team coach.

With no previous experience at the level, Diniz is struggling badly. At least in last Thursday's 2-1 defeat to Colombia, his side created chances -- they did very little of this in the previous three games. But the defensive side was a disaster. Even with his club sides, a Diniz defence can be exposed.

His Brazil side have already conceded six goals in the current campaign -- more than they let in during the entire 2022 qualifiers, and more than everyone else this time round bar the bottom two, Bolívia and Peru. And last Thursday was too much. Colombia had a barely credible 22 chances. Two-goal hero Luis Díaz alone had 10. A team that offers so many opportunities to the opposition is entering a lottery rather than playing football.

Will Diniz opt for something more conservative against the Argentines? It is a possibility. Instead of what effectively was a 4-2-4 against Colombia, there must be a temptation to play an extra man in midfield on Tuesday -- where Douglas Luiz of Aston Villa, for example, comes in for the injured Vinícius Júnior. But Diniz is just as likely to double down and go bold, with Gabriel Jesus coming in to operate in a front four with Raphinha, Rodrygo, and Arsenal clubmate Gabriel Martinelli.

It was seven years ago in this fixture that Gabriel Jesus really announced himself as an international footballer, looking way too hot for the Argentina defence to handle in Belo Horizonte. And the same could happen again on Tuesday. The fascinating aspect of this match is that it is so easy to see where each side can do damage to the other.

Argentina coach Lionel Scaloni has constructed a side basically made up of Lionel Messi and his fan club. Those around Messi will do his running for him and allow him to save himself to make his dramatic interventions. The midfield of Enzo Fernández, Alexis Mac Allister, and Rodrigo De Paul weave their patterns in possession, circulating the ball and seeking to bring Messi into the game close to the opposing goal.

And so if Brazil only play two in midfield (André and Bruno Guimarães were the pairing against Colombia), then Argentina will hope to lead them in a merry dance, playing around them and through them and exposing Brazil's weakness at full-back as the Colombians did to such good effect. It could be painful watching for the home crowd -- and the Maracana public can turn viciously against their own side.

But for all the fact that they are a consolidated team, Argentina remain a team with an Achilles heel. Were it not for a magnificent save from goalkeeper Emiliano Martínez in the last seconds of the World Cup final, then the entire narrative of Qatar 2022 -- and the biography of one of the all-time greats -- would read very differently. If Randal Kolo Muani's shot had gone in, then the story would have been that Messi had been let down by Argentina's suspect defence. The back line creaked under pressure against Australia and the Netherlands and came close to collapsing in the final against France.

True, for eight games after Qatar they did not let in a single goal. But this was always a little too good to be true -- and it had plenty to do with the lack of quality of the opposition. That run ended on Thursday. While Brazil were losing in Colombia, Argentina were going down 2-0 at home to Uruguay -- and Diniz will surely be enthused by sitting down to watch the highlights.

Uruguay were able to block Argentina and then pose a major threat on the counterattack. A couple of times, Darwin Núñez was too quick for Nicolás Otamendi. He got behind the veteran defender and charged for goal -- and the second time, he ended his run with a cool finish which clinched the three points.

Brazil lack a centre-forward with the power of Núñez. But they have plenty of pace, and slipping it behind Argentina's defensive line is where Diniz will count on winning the game and ending the year on a high. There is clearly more at stake for him than for his opponents.

Whatever happens on Tuesday, Argentina will still be ahead of Brazil in the table. True, a second consecutive defeat will be a blow to morale, but Scaloni has always been aware that he would need to replace Otamendi before the next World Cup. He will have more than two years to find a solution. It is still not clear how long Messi will be around -- but Scaloni has already had an encouraging look at Julián Álvarez as a Messi substitute.

Argentina, then, can afford to lose without it becoming a crisis. The same is not true of Brazil, for whom a first-ever home defeat in World Cup qualification would be seen as an extra dose of humiliation.