Four South American nations will battle it out for two places in the quarterfinals this Saturday, as the knockout stages of the World Cup begin. Host nation Brazil could be the first side to ensure a last-eight berth, if they pass a dangerous test against Chile.

There has been a mad frenzy on the streets of Brazil whenever the Selecao has prepared for a match. The country is hoping its players can handle the expectation levels, while Barcelona's Neymar continues his devastating attacking form with four goals.

Brazil's experienced coach Luiz Felipe Scolari has been around the blocks, winning the World Cup in 2002 and has no doubts about the mental strength of his team.

"It is understandable that one should feel uncomfortable and anxious, especially when you get to the knockout stage. We can't afford to make a mistake," Scolari said.

'A bit nervous'

"There is a bit more anxiety, more nerves. But that is normal in any competition, not just because we are in Brazil. When I am on my own and I start to think, I do get a bit nervous."

Chile have never won against Brazil on Brazilian turf, but the performances of the team at the World Cup have caught many eyes. The Chileans defeated Australia and Spain in the group phase to progress with a unique, all-out attack style of football.

Beating Spain was one thing, but providing the knockout blow to hosts Brazil is a huge ask.

"We are going to have the entire stadium against us," coach Jorge Sampaoli said. "Chile have improved a lot, we have developed a lot, nowadays we can play without fear. Chile will play to win. We don't want to be forgotten.

"Brazil already have a beautiful history, we want to make a history of our own," he added.

Sampaoli was coy about the fitness of two key midfielders Arturo Vidal and Gary Medel.

The latter is expected to miss out, but Vidal, a former Bayer Leverkusen player, could recover in time after a recurrence of the knee problem which forced him to have surgery.

Rio awaits vibrant clash:

The Maracana stadium in Rio de Janeiro could probably sell two times over, as Colombia and Uruguay battle it out for a place in the last-eight.

Both teams have been backed, so far, by raucous supporter groups and when either team has been in action, the colors of yellow and light blue have been dominant.

Things have gone sour for the Uruguayan team, however. Disgraced Liverpool striker Luis Suarez was handed a nine-match ban from FIFA internationals and a four-month suspension from all football activities. It's caused huge outrage on home soil.

"We think this will be remembered, this will remain among the worst moments in the history of football. This will be an eternal shame in the story of World Cups," said Jose Mujica, the left-wing president of Uruguay.

Meanwhile, Oscar Taberez, the head coach of the national side, has quit his position on a FIFA strategic committee, branding Suarez a "scapegoat" after his alleged bite on Italian defender Giorgio Chiellini.

The worldwide focus on Suarez's misdemeanors has taken the spotlight off the Colombians who have dazzled at the World Cup with James Rodriguez, the AS Monaco attacker, touted as the Player of the Tournament, to date.

In qualification, both teams shared the points in the two matches with Colombia trouncing La Celeste by four goals and Uruguay taking the spoils after the return clash.

The Colombians have since put to bed any doubts over their credentials following the pre-tournament injury to Radamel Falcao.

'Very delicate issue'

"Listen, at this time this is a very delicate issue," Colombia's coach Jose Pekerman responded when asked about Suarez. "But our concern is Uruguay as a team and we are working in order to play against them tomorrow.

"That's all there is to say," he added. "Whichever way you look at it, they will always be a difficult rival, whatever the circumstances."

Writing in his "El Tiempo" column, Gabriel Meluk said: "This Colombian team is magical," he … Jose Pekerman appears to just click his fingers and brings goals, triumphs, tributes and applause.

"Everything we imagine turns into reality... it made my legs tremble," said the Bogota columnist.

Colombia had never previously won more than one match at a single World Cup and only progressed beyond the group stage once, in 1990.