THERE is a taxi driver in Rio de Janeiro who has been steering his cab through the winding city streets while watching a small television fixed to his dashboard, his eyes darting towards live coverage of whatever World Cup game happens to be on.

Yes, it is every bit as absurdly risky as it sounds, not least because he often has only one hand on the steering wheel while the other presses a mobile phone to his ear.

Taking and making calls while driving seems to be mandatory for Brazilian cab drivers and simultaneously watching television adds a comical new level of madness. It is hard to believe too many health and safety laws are being observed during all of this, but then eight days in the country demonstrated that Brazil during a World Cup is a law unto itself.

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Pity any hapless passenger who gets in that driver's cab at 5pm today (1pm Rio time), although the chances are he will have clocked off long before that. He took us through Rio eight days ago during the Italy-Costa Rica game, which he presumably felt he could watch without taking any time off. Today is a different matter.

Brazil face Chile in the first of the last 16 games, the opening knock-out tie, the first game which has the potential to devastate the host nation. Having been a witness to the euphoric bedlam which envelopes Brazil when the Selecao are playing - I was in Rio when they drew with Mexio last week and in Sao Paulo when they routed Cameroon on Monday - God knows what sort of state they are going to be in if and when the team burrows deeper into the tournament.

As they ran four goals past the Africans five days ago we soaked in the scenes in Sao Paulo: air horns and firecrackers going off, people of all ages dancing in the streets, Samba music, drums, percussion, men spilling out of bars, cups of Brahma and Skol beer (the local favourites, and no it's not the same Skol) being thrown in the air. And the game itself was 525 miles away in Brasilia.

Rio de Janeiro is a mesmerising, intoxicating place, a full-on assault on the senses. One of the things that is so interesting about it, for this month at least, is the incredible number of people wearing yellow and green.

The Brazil shirt is everywhere. It must be about one in six of the population, one in eight at the very least, who are going around in the great canary yellow shirt with green trim. Kids, men, women, the elderly, restaurant staff, bar workers, drivers, shop assistants: all are living, breathing testimony to the national obsession.

Each of those shirts has five stars which elegantly arc over the badge of the CBF, the Confederation of Brazilian Football. Each wearer longs for their clothes to soon look out of date. Brazil are four victories away from having to apply a sixth star, if 2014 can be added to 1958, 1962, 1970, 1994 and 2002 as one of their World Cup-winning years.

They have not touched any great heights over their three matches so far but no other nation has been consistently excellent either and a Brazil team playing on home soil is a powerful, elemental force. The last time Brazil lost a competitive home game was against Peru in the Copa America semi-final first leg. In 1975.

Chile could knock them out. Their small, dynamic team bursts with energy and patriotism. Claudio Bravo has had a fine campaign in goal, Gary Medel anchors their midfield, Eduardo Vargas, Arturo Vidal and the magnificent Alexis Sanchez do not give defenders a moment's peace.

Their vast, vast support bellows out their national anthem like nothing you have ever heard. They did against Spain and the Netherlands, at least.

The number of Brazilian shirts in the stands during every game of this World Cup has made it seem like each fixture has two teams and three sets of fans.

There were hundreds of ticketless Chile fans outside the Arena Sao Paulo on Monday and they will have faced an almighty struggle to find a way into this afternoon's game (Brazil knew they would be playing in this one if, as expected, they won Group A, so their gigantic support has had months to snaffle up all the tickets). Tickets have been touted for almost £1200 on the black market.

On that sea of yellow jerseys one number, and one name, is printed far more than any other. Pele, Zico, Rivaldo, Ronaldinho and Kaka have all graced the No.10 shirt and now it is Neymar Jr's time. Brazil have five stars on their shirts but only one in them.

Neymar might look and occasionally act like a bit of twerp, but that cann ot disguise his skill, balance, pace and finishing ability. More impressively, he has handled the unimaginable pressure of being Brazil's poster boy and her one chance of lifting the cup.

He has scored four of their seven goals. He has delivered.

Only one opposition player scored against Brazil in the three group games, though (Croatia's consolation in their 3-1 defeat was a Marcelo own goal) and Thiago Silva leads a defence which has been hard to penetrate.

Chile took down Spain but the Brazilian juggernaut looks just too big for them. When he should have his eyes on the road, that Rio taxi driver will be looking to the quarter-finals.