The Copa America group stage was a hit-and-miss affair, with superpowers Brazil and Argentina struggling until the final game, when each team seemed to spring to life. But now we're down to the business end of the tournament when there's no margin for error. Here's a look at the key questions all eight team managers face as we head into the quarterfinals, which start Saturday.
Colombia vs. Peru
How does Dario Hernan Gomez use his wingers?
With the exception of Carlos Sanchez replacing Gustavo Bolivar in the holding midfield role after the opening game, Gomez has kept the same side and formation throughout Colombia's three games in this competition so far. The one slight difference in tactics has been the use of Adrian Ramos and Dayro Moreno, the two wingers. Not only do they both have the ability to play on either flank, meaning mid-game switches are possible, Gomez has sometimes used them very high up against the opposition fullbacks, making a 4-3-3. At other points, he has brought them back alongside the two central midfielders, meaning more of a 4-1-4-1.
In all probability, they'll play both roles, depending on whether Colombia has the ball -- Gomez's side will dominate possession, and the positioning of the wingers will dictate how aggressive it is going forward.
How does Sergio Markarian breach the Colombian defense?
Colombia is the only side yet to concede a goal in this tournament, a record made all the more impressive by the fact that it has left out the player many would consider its best defender, Cristian Zapata, who this week joined Villarreal from Udinese.
Markarian will be consoled with the fact that he has one of the tournament's few in-form strikers, Paolo Guerrero, who scored two goals in two starts before being rested for the final group game against Chile. He's been excellent at leading the line. His only mistake has been a miss late on against Uruguay, when he should have headed Juan Vargas' cross in.
Guerrero thrives off delivery from wide areas, but since he's likely to be up against 35-year-old
Mario Yepes and 32-year-old
Luis Perea in this match, he'll be better off testing them for pace. His goal against Uruguay came from a long ball over the top -- he outsprinted the center backs, rounded the goalkeeper and tapped in. A similar direct approach might be in the cards here.
Argentina vs. Uruguay
How does Sergio Batista get Lionel Messi on the ball?
Messi's performance against Costa Rica in Argentina's previous game was possibly his best-ever performance at the international level. He picked up two assists, and could have had more were it not for the woeful finishing of
Gonzalo Higuain. Batista will start with the same XI against Uruguay, meaning Higuain will start up front, Messi will play behind, with Sergio Aguero on the left flank and Angel di Maria shuttling forward from midfield. The right flank may be bare, with Messi and Higuain covering that side without the ball.
Messi will quickly be confronted with the Uruguayan duo of Egidio Arevalo and
Diego Perez in the center of midfield, however. They work excellently as a unit, and will be focused upon stopping Argentina's No. 10. He'll be confident of dribbling past them, but if Messi finds it difficult to receive the ball, does he come deeper and isolate Higuain, or move higher up and make the initial pass to him more difficult? Alternatively, does he move back to his old position on the right?
What formation does Oscar Tabarez play?
Tabarez is a tactical chameleon, having played 3-5-2, 4-3-3, 4-4-2, 4-4-1-1, 3-4-3 and a 4-4-2 diamond at one point in last summer's World Cup and this Copa America tournament. The only constant is the use of Perez and Arevalo as a double pivot in the center of midfield.
This might be a rare occasion when he can afford to stick with the same formation, however. A narrow 4-4-1-1 worked well against Mexico, as Uruguay pressed well and dominated the ball in the center of the pitch. With Argentina's fullbacks not a huge attacking threat, Uruguay can afford to play without much width.
Diego Forlan can drop deep and link play, and
Luis Suarez can use his pace to trouble Argentina's elderly center backs.
Another decision is at left-back. Tabarez has used both
Martin Caceres and Alvaro Pereira there -- the former is a better defender, but the latter is far superior on the ball, and has scored two goals in this competition. With Argentina set to either (A) not play a right-winger or (B) play the world's best footballer there, this is likely to be the key battleground.
Brazil vs. Paraguay
Which attacking combinations does Mano Menezes look to?
Menezes seems set to play the same side that overcame Ecuador in Brazil's final group game, which means Robinho starting on the right rather than Jadson, the man who started and scored in the group phase contest between these two sides.
Robinho's impact against Ecuador was negligible, and it seems strange that Menezes would choose to play a wide forward rather than Jadson, an attacking midfielder who plays much narrower. After all, Jadson combined with Ganso to open the scoring against Paraguay, and the two worked a great chance for Pato in the first half. Brazil's last-gasp equalizer also came right down the center of the pitch -- Ganso flicking the ball on for Fred. Paraguay looked most vulnerable through the middle, so the use of a wide forward would be a curious decision.
If Robinho does start, it will be interesting how Brazil plays in the final third. Will it still try to play through the middle, or will it embrace its width and play down the flanks? The fullbacks overlapping might be key -- Andre Santos crossed for Pato's first goal against Ecuador, and Maicon (in for Daniel Alves) stormed forward to assist Neymar's goal.
How does Gerardo Martino get Nestor Ortigoza on the ball?
Ortigoza, the small, stumpy and -- OK, we might as well say it -- rather plump Paraguay central midfielder has been one of the competition's star performers, dominating the midfield zone with his intelligent short passing, and sometimes knocking longer cross-field balls to the flanks to start attacks. He is likely to be the most important player in this match. Brazil can find itself a little understaffed in midfield when Ganso pushes forward and links up with the front three, and if Paraguay can get the ball quickly to Ortigoza, Paraguay can break forward and catch Brazil out on the break.
Chile vs. Venezuela
Who will Claudio Borghi play as the No. 10?
Chile started the tournament with Mati Fernandez in this position, but injury forced him to give way in the opening game against Mexico, and Luis Antonio Jimenez has played there since.
There is another contender, though: Jorge Valdivia, who actually wears the No. 10 shirt so revered in South America. He has been recovering from injury and has so far been limited to two substitute appearances, but he's still managed to show his class. A superb pass for Jean Beausejour got Chile back into the game against Uruguay, and there is an increasing feeling that Valdivia is the missing part of the puzzle.
A further decision is who should replace Beausejour on the left, after he was sent off in the final group game against Peru. He's started the past six Chile games in that position and is excellent at stretching the play on the left, making his absence a real blow.
Arturo Vidal might be the solution. He's played as a central midfielder, a left wing-back and even a left-sided center back so far in this tournament.
How does Cesar Farias instruct his side to attack?
Chile is likely to make most of the running in this game, pressing from the front and getting plenty of men forward into attack. Venezuela will spend most of the game camped in its own half. The question is, how do Farias' men form attacks of their own?
Chile seems most vulnerable to quick, direct counterattacks -- the sheer number of players it pushes forward means it's often exposed at the back. This might suit Venezuela well. Farias likes to bring his wide players,
Juan Arango and Cesar Gonzalez, into the center of the pitch quickly, turning a 4-4-2 into a 4-2-2-2, and meaning that quick forward passes are always an option.
The key factor might be how far Arango and Gonzalez track the Chilean wing-backs. If they go all the way and end up on the edge of their own box, they'll find it difficult to break. If they're a little braver and remain higher up the pitch, counterattacks will be much easier, and Venezuela could spring a surprise.
