The United States and Portugal will square off Sunday in Manaus with advancement to the next round possibly on the line for the Yanks.
Even with the draw between Germany and Ghana Saturday, Jurgen Klinsmann's men would advance to the knockout round with a victory over Paulo Bento's Portugal side, who lost to Germany on the first day of play in Group G.
With so much riding on the match, the key battles on both sides of the pitch will receive more attention than usual because of the implications.
Fabian Johnson vs. Cristiano Ronaldo
The biggest matchup on the pitch by far is the one between United States right-back Fabian Johnson and 2013 Ballon d'Or winner Cristiano Ronaldo.
Ronaldo's influence on the game against Germany melted away faster than his hair gel, and with elimination staring him in the face Sunday, he will have to provide plenty of quality for Portugal.
Johnson's showing against Ghana was nothing to write home about either, because he was unable to surge forward due to the lack of offensive firepower in the American attack once Jozy Altidore left the match.
Johnson could neutralize Ronaldo's influence on the Portugal attack by making overlapping runs on the right wing to distract the best player in the world.
Team-mate Jermaine Jones has confidence in Johnson.
“We don’t make a big deal about Cristiano,” Jones said, according to mlssoccer.com. “I think we are trying to make it our own game and if he plays on the left side, he will play against Fabian. We have trust in Fabian that he can stop him.”
Regardless of how that strategy works out, Ronaldo will find himself some space in the attacking third, and how Johnson copes with that will be key to an American victory.
Aron Johannsson or Chris Wondolowski vs. Ricardo Costa and Bruno Alves
The matchup between the American forwards and Portuguese center-backs has slightly lost its star power, as Altidore pulled up with a strained hamstring against Ghana and Pepe is suspended after being sent off for a foolish head-butt on Thomas Mueller.
With both players out, it will be up to their replacements to fill in and make an impact. Whichever reserve plays better will have a massive influence on the final score.
Klinsmann will have to decide between Aron Johannsson and Chris Wondolowski, a pair of players who possess two different skill sets, while Bento will rely on the 33-year-old Ricardo Costa to partner Bruno Alves and his 73 caps.
Both American forwards will look at the matchup with their eyes wide open thanks to the absence of the physical Pepe, but that doesn't mean the Portuguese duo in the middle of defense will lack tenacity when it comes to preventing scoring opportunities.
Jermaine Jones and Michael Bradley vs. Raul Meireles and Joao Moutinho
Four world-class midfielders will look to dominate possession in the middle of the pitch Sunday, but only one duo will be able to achieve that task.
Jermaine Jones and Michael Bradley have turned themselves into a formidable duo that can drop back and defend to earn possession, as well as surge forward in attack.
Raul Meireles and Joao Moutinho bring the same attributes to the table for Portugal, which will make the midfield battle crucial to success.
Neither midfield pairing dominated the possession battle in their first game, which will motivate them even more than usual.
The frustrations of each player will also play a role, especially Jones and Meireles, who can get a bit too physical for the referee's liking at times.
Everyone vs. Manaus
The Arena Amazonia in Manaus is located in the middle of the Amazon, which presents the players with a battle against the heat and humidity.
Per Yahoo! Sports, Italy's Claudio Marchisio, who played against England, had words of warning for both teams.
"At times it felt like [I was] having hallucinations due to the heat," Marchisio said after his team had beaten England 2-1.
In the first game played in Manaus between England and Italy, it was the Azzurri who had more stamina to survive the elements and win.
During the buildup to the World Cup, Klinsmann put a ton of focus on fitness, but that backfired in Natal against Ghana when multiple players pulled up with cramps.
Portugal did train in the United States before traveling to Brazil to prepare in a warmer climate than Europe, but most European teams have not been able to stand the heat against opposition from other continents in Brazil.
In 13 games against opponents from another continent, European sides have five wins, six losses and two draws.
Follow Joe on Twitter, @JTansey90.