Cristiano Ronaldo v Fabian Johnson
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 on Sunday, he will have to provide plenty of quality for Portugal.
Johnson's display against Ghana wasn't impressive either because he was unable to surge forward due to the lack of offensive firepower in the American attack once Jozy Altidore had 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. 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.
Raul Meireles v Jermiane Jones
During his time in England, Raul Meireles vary rarely grabbed the headlines. When he played, he was normally there to solely break up the opposition and give the ball to his more creative and forward-thinking teammates; his role is exactly the same with Portugal. The former Chelsea and Liverpool star's performance against Germany will be one he will be disappointed with, and he will know he will have to improve if Portugal are going to better that result against the USA.
Jones plays a similar role for the the USA. Energetic and aggressive, the midfielder looks to get in the faces of the opposition and tries to unsettle them with his tackling and closing down. This matchup will be interesting as to who frustrates who first, and therefore wins the battle. Don't be surprised if these two are first to be booked, as referees normally don't appreciate the aggressive style as much as Meireles and Jones do.
Bruno Alves and Clint Dempsey are both very experienced on the international stage. Alves, especially in Pepe's absence, will have to ensure Portugal's defence is far more resilient than it was under German pressure on Monday. Conceding four goals under any circumstances will do little to their confidence, and with Fabio Coentrao missing as well, Alves will have to lead a new back four against a confident USA attack.
It's not only Portugal's defence who are missing players - the USA are without Sunderland striker Jozy Altidore because of a hamstring injury. Therefore, Clint Dempsey is expected to start up front for the North American country, who will be looking to make it two wins from two before they face Group G favourites Germany in their last match. Dempsey's movement and know-how can cause Alves problems, and he will be full of confidence after his goal against Ghana.