More than 100,000 Argentine fans will besiege Sao Paulo on Tuesday to see four-time world footballer of the year Lionel Messi and his team-mates take on Switzerland for a place in the World Cup quarter finals.
Belgium meanwhile have injury worries, including captain Vincent Kompany, as they head into a match against Jurgen Klinsmann's surprise American side which closes the tournament's last 16 phase.
The Argentine football army will be in place inside and outside the stadium when the Switzerland game starts at 1600 GMT. Most will have to watch giant screens outside the Corinthians Arena.
Victory for Messi would end the career of Switzerland's legendary German coach Ottmar Hitzfeld who has said he will retire at the World Cup.
A win for Hitzfeld's team would be a major upset and a disaster for the world superstar now in his third World Cup without ever getting close to touching the trophy.
And despite a frontline that also includes Gonzalo Higuain and Angel di Maria, and until his injury Sergio Aguero, Argentina are susceptible to their reliance on Messi.
Their three Group F wins over Nigeria, Iran and Bosnia-Hercegovina all relied on Messi goals -- four out of the six scored by Argentina.
Argentine coach Alejandro Sabella said he was happy for the two-time world champions to rely on their star man and likened it to Brazil using Messi's Barcelona team-mate, Neymar.
"I think both players are amazing. Messi's the best in the world, Neymar is a great player and of course with players like this the team depends on them. It's normal," he said.
Switzerland are calling Xherdan Shaqiri -- who scored all the goals in the 3-0 triumph over Honduras -- their own Messi. But Switzerland have never beaten Argentina at the World Cup in six previous attempts.
And despite scoring seven goals in Group E, they also conceded six, including five by France.
- Late Flight Home -
Belgium could be without captain and centre-back Kompany and are definitely deprived of his central defensive partner Thomas Vermaelen. who has a knee injury, when they take on the United States in Salvador at 2000 GMT.
Kompany is struggling with a niggling groin injury, but coach Marc Wilmots still said it would be a "failure" not to reach the quarter finals.
He was also unconcerned about criticism of the style of Belgium's three straight wins in Group H and playmaker Eden Hazard being eclipsed in most matches.
"I let people make their complaints, we just advance. We are not going to bang our heads against the wall. When I see the team giving everything I have no regrets. We have a young team, unbeaten for a long time in competitive matches," Wilmots said Monday.
Klinsmann, who faced criticism from the US media before the tournament but is now flavour of the moment, is also confident.
He has told his players to push their flights back to after the July 13 final.
Belgium beat the United States in two friendlies in the past three years. But Klinsmann says the US team has changed as they showed with their group win over Ghana and determined draw with Portugal.
"We also believe we can have enough confidence going into this very special knockout game to say we are able to beat them," said the German.
The winners of the two games will clash in the quarter finals in Brasilia on Saturday.