While few doubt Germany and Portugal, second and fourth respectively in the FIFA World Rankings, would eventually make it through from Group G to the knock-out stage, Ghana and the United States are hoping to produce some upsets.

All the four teams advanced to the last 16 in the World Cup four years ago, so none would be satisfied with an early exit.

Germany is considered as the most consistent national team in the past decade, making into the final four in all of the previous three World Cups. Their squad is filled with youth power and energy, averaging 24.8 years old. The veterans, such as Miroslav Klose (36), Roman Weidenfeller (33) and Philipp Lahm (30) will also bring their experience.

While Germany looks safe for a last of 16 berth, Portugal may not have a plain sailing. The Portuguese qualified for this year's World Cup via a play-off after coming second in their group behind Russia.

Their superstar Cristiano Ronaldo, who scored four goals in Portugal's 4-3 win over Sweden in the playoffs, needs to prove himself on the World Cup Stage. The La Liga top scorer netted only twice in his 11 World Cup matches, including one penalty.

As a top team in the world, Portugal is far more than Ronaldo's one-man team. Both Bruno Alves and Pepe are world-class defenders, and Rafa Silva, Raul Meireles, Miguel Veloso and Raul Meireles will form a strong midfield to support Ronaldo.

Jurgen Klinsmann faces extra pressure in Brazil as he dropped US all-time leading scorer Landon Donovan out of America's 23-man squad for the World Cup, a decision that has been widely questioned.

The US team, ranked 14th in the world, will rely on a strong midfield with Michael Bradley and Jermaine Jones while Jozy Altidore and captain Clint Dempsey must score goals if the US want to advance.

Ghana failed to become the first African team to make the World Cup semis in 2010, but their victory over the United States in the knockout round will boost their confidence in Brazil.

Sulley Muntari, Kwadwo Asamoah, Michael Essien and Kevin-Prince Boateng will keep the Ghana midfield among the best in the 32 teams.