Shamoon Hafez
BBC Sport at Lusail Stadium

Don't shout it too loudly, but the Saudis have taken over Qatar.

It's a tsunami of green and white with an estimated 150,000 fans crossing the border on the three hour drive to reach Doha for their crunch clash against Mexico. I'm told around 60,000 will be at the game tonight.

Victory will take Saudi Arabia into the knockout stage for the second time since 1994.

There were some very nervous faces on the metro to Lusail and the lads sitting next to me very pensive, shaking his head and probably feeling sick to his stomach.

I asked him if the Green Falcons will win today and he simply replied: "Inshallah, Inshallah."

Image source, BBC Sport

Image source, BBC Sport

BBC Analysis editor Ros Atkins looks at how Qatar won the World Cup, as well as the human rights and environmental issues surrounding the tournament...

Image source, Getty Images

An all-female on-field refereeing team will take charge of a men's World Cup game for the first time in Thursday's group-stage game between Costa Rica and Germany.

Stephanie Frappart will be the first woman to referee at a men's World Cup.

The Frenchwoman became the first female official at the tournament when she was named as the fourth official for Mexico and Poland's game last Tuesday.

"We know the pressure," Frappart told BBC Sport before the tournament.

"But I think we will not change ourselves. Be calm, focused, concentrate, and don't think too much about the media and everything, just be focused on the field."

Frappart will be joined by assistant referees, Brazil's Neuza Back and Mexican Karen Diaz Medina, at Al Bayt Stadium on Thursday.

Read more here.

Image source, BBC Persian

Anti-government protesters in Iran have been celebrating the national football team's elimination from the World Cup, following their 1-0 loss to the USA.

Videos showed people dancing in streets and honking car horns in Tehran and several other cities on Tuesday night.

Many Iranians refused to support their football team in Qatar, seeing it as a representation of the Islamic Republic.

State-affiliated media blamed hostile forces both inside and outside Iran for putting unfair pressure on the players.

The players did not sing the national anthem before their first game, a 6-2 defeat by England, in an apparent expression of solidarity with the protesters.

But they did sing at the Wales game, which they won 2-0, and at the politically-charged showdown against the USA.

Some protesters saw that as a betrayal of their cause even though there were reports that the team came under intense pressure from Iranian authorities.

Read more here.

Phil McNulty
BBC Sport chief football writer at Stadium 974

Argentina fans are here in their thousands at Stadium 974 and are already making themselves heard with a huge noise. Lionel Messi revived their World Cup campaign when they beat Mexico after the shock against Saudi Arabia - now they are looking to complete the recovery and reach the last 16 in front of their fanatical supporr.

Andy Cryer
BBC Sport in Qatar

Image source, BBC Sport

Image source, BBC Sport

It’s Stadium 974 tonight and it feels big!

Surely Argentina can’t get knocked out of the World Cup at the first hurdle can they?

Shamoon Hafez
BBC Sport at Lusail Stadium

With the turnstiles still closed, Saudi Arabia fans were offering Maghrib (sunset) prayers outside the stadium.

To paraphrase former England captain Eoin Morgan, will Allah be on their side tonight?

Poland v Argentina will draw most eyes I imagine tonight, with the Messi and Lewandowski factor running alongside the very real prospect of one of the big guns dropping before we even get to the knock-outs.

But ignore Saudi Arabia v Mexico at your peril. That is going to be a proper battle between a nation who have made the last 16 in each of the previous seven World Cups, dating back to 1994, and another who has made the biggest splash of their humble football history at this tournament and are desperate to reach the World Cup knockout rounds for only the second time (having previously done so at USA '94).

It is very much a night made to double screen.

Image source, Getty Images

Poland and Argentina are the top two in the group following 2-0 wins over Saudi Arabia and Mexico respectively on Saturday.

But those two meet in tonight's group decider, meaning there is a decent chance either Lionel Messi or Robert Lewandowski go out.

Poland would be guaranteed progression with a draw, while Argentina will go through if they win. Both sides will go through if both games are drawn.

Saudi Arabia will secure their shock entry to the knockout stage if they beat Mexico.

Mexico need to beat the Saudis to have any hope of going through. They would be through if both they and Poland win. Any other result in the other game would probably mean the Mexicans would need to win by a few.

I'm sure there will be a fair few of you here with the aim being to do a bit of rubbernecking at Argentina's expense.

Lionel Scaloni's side are very much alive and kicking in this World Cup, but have put themselves in the firing line with their opening 2-1 loss to Saudi Arabia.

One of the pre-tournament favourites, they returned to some kind of form - which had previously seen them go 36 matches unbeaten - with a win over Mexico.

But they've still got work to do in a Group C that is wide open.

Shamoon Hafez
BBC Sport at Lusail Stadium

Image source, .

Saudi Arabia make three changes to the team that lost 2-0 to Poland in their previous game.

Sultan Al Ghannam, Hassan Al Tambakti and Ali Al Hassan come in with Mohammed Al Burayk, Abdulelah Al Malki and Al Naji dropping out.

Captain Salman Al Faraj has returned home after injury ruled him out of the remainder of the tournament.

Saudi XI: Al Owais, Abdulhamid, Al Amri, Al Bulayhi, Al Ghannam, Al Tambakti, Al Brikan, Al Hassan, Kanno, Al Dawsari, Al Shehri.

Image source, .

Mexico also make three changes to the side that lost 2-0 to Argentina.

Jorge Sanchez, Orbelin Pineda and Henry Martin come in for Nestor Araujo, Hector Herrera and Andres Guardado.

Mexico XI: Ochoa, Alvarez, Sanchez, Montes, Moreno, Gallardo, Chavez, Pineda, Lozano, Vega, Martin.

Poland make just one change to the side who beat Saudia Arabia last time out. Forward Karol Swiderski comes in for Arkadiusz Milik.

Poland XI: Szczesny, Bereszynski, Kiwior, Glik, Cash, Frankowski, Krychowiak, Bielik, Zielinski, Lewandowski, Karol Swiderski

Argentina make four changes to the team who beat Mexico 2-0 on Saturday. Cristian Romero, Nahuel Molina, Enzo Fernandez and Julian Alvarez come in.

Lisandro Martinez, Gonzalo Montiel, Guido Rodriguez and Lautaro Martinez all drop to the bench in this must-win match.

Argentina XI:Martinez, Acuna, Otamendi, Romero, Molina, Fernandez, Rodrigo De Paul, Mac Allister, Messi, Di Maria, Alvarez

Robert Lewandowski made his Poland debut on 10 September 2008 in a 2010 World Cup qualifier against San Marino.

He came off the bench in the 59th minute. He scored in the 67th.

Since then, he has played 136 games for his country and scored 77 goals - comfortably the most anyone has ever scored for Poland, with Wlodzimierz Lubanski the nearest to him on 48.

Arguably, the finest number nine in modern European football, he has only once made it past the group stage of a major tournament with his country, at Euro 2016.

When his country needed him most, in their last game against Saudi Arabia, he came up with the goods.

His nation will again be looking to him to guide them into the last 16.

Lionel Messi made his Argentina debut on 17 August 2005 in a friendly against Hungary.

He came off the bench in the 63rd minute. He was sent off in the 65th.

Since then, he has played 167 games for his country and scored 93 goals - comfortably the most anyone has ever scored for Argentina, with Gabriel Batistuta the nearest to him on 52.

Arguably, the finest player ever to grace a football field, he has not always shone for his country, with the World Cup the one major trophy missing from his jam-packed and glittering collection.

When his country needed him most, in their last game against Mexico, he came up with the goods.

His nation will again be looking to him to guide them into the last 16.

Image source, Getty Images

Image source, gett

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Tonight could represent the final World Cup game for one of the world's finest international goalscorers.

Savour them this evening, people. You'll miss them when they're gone.