Costa Rica's fightback to earn a point against Turkey on Sunday means a draw, or maybe even a narrow defeat, against Brazil in their final World Cup group game will secure a second round berth.
The Brazilians, with six points, are already through and a draw in Thursday's match would be enough for the top spot in group C, but Costa Rica coach Alexander Guimaraes says any talk of Brazil doing their fellow Latin Americans a favour is ridiculous.
"The fact that they have already qualified might mean we have more of a chance," said the Brazil-born Guimaraes.
"But any suggestion that they will not try to win is ridiculous. There is no chance at all that they will do something like that, absolutely none."
Brazilian defender Roberto Carlos also said the four-times world champions would do their utmost to keep their winning run going in Suwon following victories over Turkey and China.
"For us it is very important to beat Costa Rica and get nine points," he said. "To win is important for the confidence of the team and that's why it remains an important game."
However, Brazil coach Luiz Felipe Scolari has indicated he might rest one or two players with slight knocks, Roberto Carlos included, or yellow cards to avoid a one-match suspension for the next phase that would follow a second booking.
Whatever happens, it will be an emotional moment for Guimaraes. Having played for Costa Rica against the country of his birth in a 1-0 first round defeat in the 1990 World Cup, he now leads the team against them.
"It's going to be very special for me," said Guimaraes, a naturalised Costa Rica citizen. "I think I am the first Brazilian-born person to play against Brazil and coach against them and I'm very excited."
Guimaraes said he would delay any thoughts about team selection until assessing his players' recovery from their draining game against the Turks, which finished 1-1.
But he said he was pleased with their fitness, highlighted by their strong finish.
Substitute Winston Parks forced an equaliser four minutes from time following sustained pressure and should have won it for his side in injury time, shooting into the side-netting with the empty goal gaping.
"We worked really hard but what really pleased me was the character of the team," said Guimaraes.
"We are improving with each game and as the players get more experience they get more trust in themselves."
Costa Rica were certainly extremely tentative in the first half against the Turks, as they had been before eventually getting past China 2-0 in their opening game. But they showed terrific spirit in the latter stages.
"If we show the same passion against Brazil then we have a good chance of making it to the second round," said Guimaraes."