USA. Brazil. It's the most anticipated Women's World Cup quarterfinal ever and it looks on paper to be an absolute toss-up.

Both teams are yet to meet their full potential - or at least what critics are demanding of them - and could hit their strides on Sunday, which promises to be an absolute battle.

For the United States, containing Marta is critical, but it is important not to overlook a very creative supporting cast. The Americans are 23-2-2 all-time against Brazil, but recent meetings have seen much greater balance (as well as larger profiles.

Brazil has fallen to the United States in the last two Olympic gold medal games, but perhaps more importantly, the Brazilians took down the Americans 4-0 in the infamous 2007 Women's World Cup semifinal that saw then head coach Greg Ryan play Briana Scurry in goal instead of Hope Solo.

Solo will be in goal this time around and she will serve as the last line of defense against the three prong Brazilian attack of Marta, Cristiane and Rosana. Stopping those three quick, technical players won't be easy for an American defense that apart from right back Ali Krieger is slow and prone to awkward challenges (as seen against Sweden).

Player for player, the Brazilian attack is far superior to a solid but still at times unconvincing US defense. The variable to the US defense is just how much of a hero Solo can be on a given night.

Brazil goalkeeper Andreia makes a save as her teammate Aline, left, looks on during the group D match between Australia and Brazil at the Women's Soccer World Cup in Moenchengladbach, Germany, Wednesday, June 29, 2011. (AP Photo/Frank Augstein)

Where the United States can take advantage of Brazil is on the flanks. Brazil's three-back, man marking system has been successful up to this point. But it is also yet to face any real threat offensively.

Norway proved to be more mystique than talent, and Equatorial Guinea, while a quality opponent, never proved to be a consistent threat. Australia, the second best team out of Group D, is solid but lacks the quality of the United States, especially in the Matildas' mistake-ridden defense.

The biggest difference between those teams and the US is out wide, where the US will have speed unlike any other team Brazil has seen this year. If Brazil Head Coach Kleiton Lima sticks to a 3-4-3, Erika, Aline and Daiane (or possibly Renata Costa), those three defenders will be pre-occupied with Abby Wambach and a speedy Amy Rodriguez, allowing Heather O'Reilly and Lauren Cheney (as well as Alex Morgan and Megan Rapinoe, likely off the bench) to make penetrating secondary runs in what should be very open space out wide and in behind.

The US has to take advantage of that space on the outside and draw the Brazilian back line out and break the team's shape. Abby Wambach likes to check very deep to the ball, so if she is followed into the midfield, Cheney, O'Reilly or even Carli Lloyd could overlap without getting tracked by a midfielder.

Interestingly, Brazil should also be able to find success wide, at least on the left side of the US defense where Amy LePeilbet has shown that she is not comfortable as an outside back. A true three forward attack is something that the US is not used to seeing, so it should serve as a challenge to Christie Rampone and company.

Marta will look to run at Rampone and Rachel Buehler in the center but could face a stiff test on the right in Krieger, who is emerging as the team's best defender. Marta typically likes to drift to the left, which the US might prefer given Krieger's steady play at right back.

With both back lines facing serious pressure, this game will be won in the midfield. At 33-years-old, Formiga is aging but still highly effective in possession for Brazil. Combined with Ester in the middle, Lloyd and Shannon Boxx (or Lori Lindsey) will have their hands full as center midfielders.

Fabiana is one of the most underrated right midfielders in the game. She is versatile as a right back or right midfielder, making her perfect for the role of covering the entire right flank and sliding in on the weak side when necessary. Fabiana is the perfect hybrid of defender and attacker to try to contain Cheney, who should again feature on the left side of the US midfield. Cheney won't track back to mark Fabiana, but she will keep the Brazilian honest.

However, the left side of Brazil's midfield, manned by the Western New York Flash's Maurine, is suspect. O'Reilly can take advantage of Maurine on that flank, making the midfield battle, on paper, a push. It's advantage US on O'Reilly's flank, advantage Brazil in the middle and likely a push on the opposite flank, where Cheney or Rapinoe could offset Fabiana.

So what does that tell us? It tells us what we already knew: The biggest match-up of the quarterfinals will be an even, gritty battle that could go either way between two of the world's three top teams. One team has to go home far earlier than it ever anticipated.