Japan, a vastly improved team compared to their form in the qualification campaign, will want to turn on more of their recent free flowing style and set-piece quality to beat Paraguay -- one of the less convincing Latin American sides.
But they will have to overcome a powerful jinx -- no Asian team have ever beaten a South American side in the World Cup.
Paraguay, looking to join Brazil, Argentina and Uruguay in the last eight, are yet to show the bite expected of their top class attacking trio of Roque Santa Cruz, Lucas Barrios and Nelson Valdez.
In Tuesday's second match, Spain will aim to reproduce the classy close-passing style with which they beat Chile 2-1 in their last group stage match, after a feeble start to the World Cup for the pre-tournament favourites.
But while striker David Villa has been deadly, netting three times, his attacking partner Fernando Torres has yet to reach his devastating best after returning from knee surgery.
He missed several good chances against Chile, and a powerful strike force will be needed to penetrate Portugal, who have yet to concede a goal.
Five-time winners Brazil finally turned on the Samba power on Monday night to crush traditional victims Chile 3-0 and set up an enticing quarter-final on Friday with the Netherlands, who swept aside giantkillers Slovakia 2-1.
PORTUGUESE AT HOME
The Portuguese will feel well at home for the match against Spain in Cape Town's majestic Green Point stadium, where they routed North Korea 7-0 in this World Cup's highest score.
Influential Spanish midfielder Xabi Alonso had been doubtful after spraining an ankle against Chile but coach Vicente del Bosque said on Monday he could be fit.
While Spain's clean passing style has left them without a single caution, the Portuguese have seven players on yellow cards including Cristiano Ronaldo, the world's most expensive player, who has yet to live up to his billing at the World Cup.
The winners of the Iberian clash go into the match knowing they will have one of the easier quarter-finals against Japan or Paraguay in the last eight.
Japan's Blue Samurai have been one of the revelations of the tournament with a free-passing style and mastery of the Jabulani ball in spot kicks that has eluded other more established teams.
Striker Keisuke Honda and Yasuhito Endo scored stunning free kicks in their victory over Denmark in the group stages.
While Japan look on fire, Paraguay stuttered to a 0-0 draw with lowly New Zealand in their final group game.
But coach Takeshi Okada warned against complacency and emphasised the responsibility his country was carrying for their continent. "As the only remaining Asian team at this level we really would like to get to the last eight," he said.
The Netherlands, the only European team with a perfect record so far, smoothly eliminated giantkillers Slovakia on Monday in a 2-1 victory that included a sublime goal by winger Arjen Robben, who started for the first time.
Despite strong defending by Chile, Brazil scored three fine goals through Juan and Luis Fabiano in the first half and Robinho after the break. It was their eighth victory in a row against Chile.
As England limped home in disgrace after a performance some regarded as their worse in World Cup history, the disgrace of their neighbours France claimed the head of the country's soccer federation, Jean-Pierre Escalettes, who announced his resignation.
France left last week after finishing bottom of their group following a players' revolt.
South African immigration officials have stopped 613 "undesirable" people from entering around the World Cup, they said on Monday. They did not say how many were potential hooligans but have worked closely with foreign police to keep out known troublemakers.
Villa on song as Spain beat Chile to take top spot
Audacious Chile pay for attacking Brazil
Football images: Japan vs Cameroon
Paraguay through after New Zealand draw
Spain defender Albiol injured in training