Brazil's three goalkeepers are the first to emerge from the Estadio Nacional tunnel and are greeted by a huge roar by the thousands already inside. Deafening. The trio - Julio Cesar, Jefferson and Victor - make time to pose for a prized photo with a disabled boy in the tunnel, before striding out to applaud all four corners of the ground. These lads look focused.

Away from Group A, England midfielder Frank Lampard has been chatting to the media ahead of Tuesday's dead-rubber against Costa Rica.

And Lampard says he does not know of any players who have tried to skip England duty. It comes after Harry Redknapp - Lampard's uncle - made the claims about some of his former Tottenham players.

"I certainly don't know of any players at the present who have done that." he says. "If there are any individuals who feel like that then I'm sure their careers won't be anything to write home about. If that's your attitude you won't get very far. I've never heard of it, and I'm sure Harry Redknapp's not lying, it's highly irregular and I've never met them."

David Ornstein
BBC Sport

"Cameroon are unable to qualify for the knockout stage following a campaign that's frankly been disastrous. They've been anything but Indomitable Lions in Brazil, yet there are a scattering of their supporters here and they will hope to at least restore pride after defeats against Mexico and Croatia."

Brazil defender David Luiz on Twitter:, external "We are playing in our capital city. A victory will help us to step into the second stage even stronger. Come on Brazil!"

We're also seeing pictures of the Brazil bus arriving at the Estadio Nacional a short time ago - the coach's engine is humming like the Pied Piper as thousands of Selecao supporters skip after it.

Image source, Reuters

These World Cup fans aren't the type to turn up minutes before kick-off, making a late dash from the shuttle bus and through the turnstiles just in time for the referee's whistle. Nope, thousands are already stood in position at both the Estadio Nacional in Brasilia and the Arena Pernambuco in Recife.

The former is a sea of Brazilian yellow as the Cameroon players make their way on to the pitch, while there are plenty of Mexican somberos at the latter.

BBC World's Alex South reporting in Brasilia: "This homage to the sticker album isn't too far off the expected starting line up. Luis Felipe Scolari said in his press conference that the team that started against Croatia in the opening game will be the same that takes on Cameroon.

"If that's the case it will also be exactly the same 11 that took to the field at this very stadium a year ago in the Confederations Cup. On that day Scolari's team won 3-0 against Japan - what he would give for that shoreline today."

Cameroon starting XI: Itandje, Nkoulou (c), Nguemo, Moukandjo, Aboubakar, Bedimo, Choupo Moting, Mbia, Enoh, Matip, Nyom.

Brazil starting XI: Julio Cesar, Dani Alves, Thiago Silva (c), David Luiz, Marcelo, Hulk, Paulinho, Fred, Neymar, Oscar, Luiz Gustavo

Croatia starting XI: Pletikosa, Vrsaljko, Pranjic, Perisic, Corluka, Lovren, Rakitic, Modric, Srna, Mandzukic, Olic.

Mexico starting XI: Ochoa, Rodriguez, Marquez (c), Herrera, Layun, Dos Santos, Moreno, Guardado, Peralta, Aguilar, Vazquez .

Permutations was one area of GCSE maths that no-one liked. But in tournament football it is an essential skill. Here's what the teams needs to do tonight (in a simplified format)...

Brazil: Through with a win or a draw against Cameroon. Could lose and still qualify if Mexico beat Croatia.

Mexico: Through with a win or a draw against Croatia.

Croatia: Through with a win against Mexico, or a draw if Brazil lose against Cameroon.

Cameroon: Already eliminated.

Want to impress your mates by explaining all the potential outcomes to them? Become the pub World Cup expert by going to our handy permutations piece to find out how teams in each group can qualify.

BBC World's Alex South reporting in Brasilia: "Brasilia may not have the allure of Rio but Brazil like playing in the capital. The Selecao have played here 10 times, winning eight, drawing one and losing only the once. That defeat came back in 1985 to Peru."

As David rightly says, no-one in Brazil is even contemplating a defeat for the host nation. The Selecao have only twice failed to advance from the group stage: in 1930 and 1966.

But what do you think? Is a Brazil win a foregone conclusion? Or can Cameroon cause the mother of all shocks tonight? And if Brazil do progress, who will join them out of Mexico and Croatia?

Let us know on Twitter using #bbcworldcup, text 81111 or by posting on our Facebook page., external Go on, you know you want to.

David Ornstein
BBC Sport in Brasilia

Image source, @bbcsport_david

"Welcome to Estadio Nacional in Brasilia, where for the next few hours the hopes of a nation will rest. Brazil and its people fully expect to beat Cameroon - preferably in style - to qualify for the last 16 as Group A winners. Anything less than victory will not go down well and defeat doesn't even bear thinking about. The crowds were queuing in lines as far as the eye could see to enter the ground, singing and dancing while they waited, and they're now piling in to create a sea of yellow and green inside this incredible bowl - reportedly the second costliest football venue ever built."

See the atmosphere for yourself. Here's David's video from outside the stadium ahead of kick-off., external

Ola! And a warm Brazilian welcome to the final scene of this Group A blockbuster. Boy, do we have a cliffhanger for you.

Basically everything is there to play for. Group leaders Brazil need a positive result against already-eliminated Cameroon to reach the second stage, while second-placed Mexico take on Croatia with both knowing they can still progress.

Cameroon v Brazil (21:00 BST)

Croatia v Mexico (21:00 BST)

It sounds like a movie synopsis doesn't it? But Brazil not progressing from Group A would be the sort of plot that even Hollywood scriptwriters would think is too far-fetched. In the next couple of hours, the unthinkable might well become a reality.

"That will never happen!" - I hear you cry. You are probably right. But that's the beauty of this World Cup.

Who thought Spain would be on an early plane back across the Atlantic? Who reckoned the USA would be on the verge of sending Portugal back with them? The unexpected has almost come to be the expected over the past 11 days.

Armed with the knowledge that an entire nation's hopes rest on their shoulders, 11 men from Brazil are on an important mission. Led by an experienced coach (Luiz Felipe Scolari) and an enigmatic youngster (Neymar), this crack squad of footballers are determined to bring joy to millions of their compatriots by winning the world's biggest football tournament. They call it 'Operation World Cup'.

Image source, Reuters

The Brazilian troops outfoxed a well-drilled European army (Croatia) in their opening battle. Then, an old enemy (Mexico) prevented them rampaging through to the next phase of their mission.

Now only the weakest of opponents (Cameroon) can stop them. Should they be overpowered then an entire nation will be left devastated. Brazil will be out of a home World Cup at the first stage.

Welcome to The Unthinkable.

Croatia head coach Niko Kovac could recall Mateo Kovacic in place of Brazil-born midfielder Sammir, one of the few players who failed to impress in the 4-0 win over Cameroon.

The team is likely to be otherwise unchanged for a game that Croatia will probably need to win to qualify.

Mexico boss Miguel Herrera has suggested he will go with the same line-up for the third game in a row.

Hector Moreno, Jose Vazquez and Paul Aguilar are one booking from a ban.

Alex Song is suspended for Cameroon following his sending off for elbowing Croatia's Mario Mandzukic in the back.

Benoit Assou-Ekotto headbutted team-mate Benjamin Moukandjo in that match and is unlikely to play, while Samuel Eto'o (knee) remains doubtful.

Brazil forward Hulk has overcome a thigh problem.

The quartet of Neymar, Thiago Silva, Luiz Gustavo and Ramires will trigger a one-match ban if booked for the second time in this tournament.