This does not do justice to the other quarterfinals, with Nigeria - perhaps the best team so far - against France, host country Colombia against Mexico and six-time champion Argentina facing Portugal.
Brazil and Spain have the name recognition inherited from their senior teams. Brazil has won the senior World Cup five times - more than anyone else - and Spain is the defending champion. Spain's quick passing style and possession game are being copied by the U-20 team led by Sergio Canales and Alvaro Vazquez.
''I don't think this should be seen as the final everyone was anticipating because there are other top quality teams like Colombia, Argentina and Nigeria,'' Brazil coach Ney Franco said. ''But, yes, one of the finalists could come out of this match. We're going against a team with tradition and the defending World Cup champions.''
Despite Franco's words, Brazil may have the edge on Sunday although it has been playing the tournament without top stars Neymar and Lucas, who were with the senior national team in the Copa America last month in Argentina.
The South Americans, looking for their fifth U-20 title, routed Saudi Arabia 3-0 in their round-of-16 match and have scored 10 goals and allowed just one in four matches. Henrique and Philippe Coutinho have each scored three times.
Spain, which won the title in '99, was pushed to the edge in its victory over South Korea, winning 7-6 in a penalty shootout after 120 minutes of scoreless football. Vazquez leads with four goals and Canales has two.
''We have stayed faithful to our playing style, and it's been rewarded,'' Spain goalkeeper Fernando Pacheco said. ''We have to think game to game. Every game is like a final and we'll have a very tough match in the quarterfinals.''
The winner will face the winner of Sunday's other quarterfinal between Nigeria and France.
Nigeria, which has finished the runner-up twice, is the slight favorite behind an attack that has scored 13 goals. The west Africans are only one of two teams with a perfect record - host Colombia is the other. Three players have scored three times: Ahmed Musa, Olarenwaju Kayode and Edafe Egbedi.
France will be trying to advance past the quarterfinals for the first time. The French have come back from a 4-1 opening-match loss against Colombia, perhaps adjusting to playing at altitude in Colombia.
One of Saturday's quarterfinals will attract much of the home nation's attention with Colombia going against Latin American rival Mexico.
The Colombians will play their fifth straight match in Bogota, where the altitude of 2,600 meters (8,600 feet) has undoubtedly been an advantage. But it will not make much difference against Mexico, where many cities are located in high mountain valleys, including Mexico City at an altitude of 2,250 meters (7,400 feet).
Colombia's capital Bogota is awash with street vendors selling yellow, blue and red Colombia shirts, vuvuzelas and other trinkets. The event has been well organized with local politicians touting the country as a potential venue for the senior World Cup.
Colombia is led by Luis Muriel, who has scored four times, and teammate James Rodriguez with three goals. Rodriguez coolly converted the penalty that was the deciding goal in the 3-2 victory over Costa Rica in the round-of-16.
''The teams are very even with excellent players,'' Mexico winger Cesar Ibanez said. ''We are going to be watching James (Rodriguez). He is a good passer and we'll be marking him so he does not hurt us with his assists or goals.''
Argentina's performances have slipped under the radar. But the six-time champions - they have won five of the last eight titles - cannot be underrated despite scoring only six goals in four matches. Erik Lamela has three - two via penalties - but could be doubtful with a left-ankle injury.
''I'm playing with pain, but I think it will be better with rest,'' Lamela said.
Portugal has scored only three goals and may have more trouble on Saturday. Nelson Oliviera has two of the goals with Mario Rui getting the other. Rui will miss the match after collecting his second yellow card.
Stephen Wade can be followed at http://twitter.com/StephenWadeAP