By DAVID MOSSE

It would be disrespectful to six-time champions Argentina to call the upcoming quarterfinal clash between Spain and Brazil the decisive match of the Under-20 World Cup, but the winner will have incredible momentum heading into the semifinals.

Spain should feel somewhat fortunate after needing a penalty shootout to vanquish South Korea on Wednesday following a scoreless draw. Julen Lopetegui's side dominated the match, but it was unable to put anything past goalkeeper No Dong Geon, with Daniel Pacheco and Rodrigo particularly wasteful. The shootout was eventually decided when Kyung Jung sent his spot-kick sailing over the crossbar.

Brazil, meanwhile, struggled for a half against Saudi Arabia before the introduction of William Jose in place of Casemiro jumpstarted a sluggish attack.

A brilliant back-heel from the Sao Paulo hitman set up Henrique for the opener, while goals from Gabriel Silva and substitute Dudu sealed the 3-0 victory for a Brazilian side rounding into shape at the right time. Questions remain in the center of defense and Ney Franco should consider moving Danilo back to right back, giving his team more width offensively, but Philippe Coutinho and Oscar continue to shine.

Argentina can count on the brilliance of Erik Lamela, who scored both goals from the penalty spot in the 2-1 win over Egypt. Lamela is now the main attraction with Juan Iturbe no longer commanding a starting place in Walter Perazzo's side, and the former River Plate starlet will need to be at his best against Portugal in the next round. The Lusitanians got past surprisingly plucky Guatemala 1-0 on Tuesday.

Mexico overcame Cameroon in a shootout after Franck Ohandza and Carlos Orrantia traded goals in the final 11 minutes of regulation, while hosts Colombia survived a major scare against Costa Rica. Trailing 2-1 late in the second half, Los Cafeteros equalized through Pedro Franco and grabbed the winner from the penalty spot in stoppage time, courtesy of influential midfielder James Rodriguez.

Nigeria continued its impressive campaign with a fourth straight victory, knocking off toothless England in the dullest match of the round. Edafe Egbedi notched the winner seven minutes into the second half, setting up a highy-anticipated confrontation with France, which had a difficult time with Ecuador. The Europeans claimed a 1-0 victory they barely deserved thanks to a second-half goal from Antonie Griezmann.

Here is a closer look at the quarterfinal matchups:

Portugal vs. Argentina: Saturday, 6 p.m., ESPNU

Nelson Oliveira converted a penalty kick for the only goal of the match in the 1-0 win over Guatemala, and he has emerged as the most influential figure offensively for Portugal, but Oliveira will need help and striker Alex is suspended due to yellow-card accumulation. The back line remains solid thanks to captain to Nuno Reis.

Argentina has quietly gone about its business without playing sparkling soccer. Lamela and Iturbe – if he can regain his place in the starting XI – are potential match-winners, while Carlos Luque is a dangerous player as well. The defense has conceded only one goal and Roberto Pereyra returns from suspension on Saturday.

Mexico vs. Colombia: Saturday, 9 p.m., ESPNU

Chivas standouts Ulises Davila and Erick Torres have struggled to impose themselves so far with Torres even losing his place in the starting lineup, but both players held their nerve in the shootout against Cameroon. Juan Carlos Chavez will hope it sparks a turnaround because Mexico must improve its finishing to advance any further.

Hosts Colombia, meanwhile, are difficult to contain offensively with Rodriguez pulling the strings. Luis Muriel is a dangerous striker and captain Pedro Franco contributed a goal in the come-from-behind 3-2 win over Costa Rica. Los Cafeteros count on tremendous crowd support and will be confident of overcoming Mexico.

France vs. Nigeria: Sunday, 4 p.m., ESPNU

France has disappointed so far with expected stars like Gael Kakuta and Yannis Tafer no longer even assured of a place in the starting XI, but Francis Smerecki’s side continues to progress. Next up is a clash with arguably the most impressive team in the competition, as Nigeria has won all four matches, scoring 13 goals.

Edafe Egbedi notched the winner against England and is one of three players who have already found the back of the net three times along with Ahmed Musa and Olarenwaju Kayode. Uche Nwofor has added two goals and boss John Obuh deserves credit for his attack-minded approach, but Nigeria could be vulnerable at the back.

Brazil vs. Spain: Sunday, 7 p.m., ESPNU

Such is the wealth of talent possessed by Brazil and Spain that players like Neymar, Thiago Alcantara and Lucas Moura could be left out of this tournament, and the two teams still look capable of going all the way. Only one will advance past the quarterfinals, however, and the South Americans must beware of Sergio Canales.

Rodrigo and Alvaro Vazquez are also significant threats, but Brazil counters with some firepower of its own. Henrique has scored three times, benefiting from the delicious service provided by Philippe Coutinho and Oscar, while Danilo is always bursting into the opposition penalty area no matter which position he occupies.