It's on: The World (Cup) comes to Brazil for soccer supremacy

The World Cup features eight groups of four teams each. The teams in each group play each other once, with the top two from each group advancing to the round of 16 knockout stage. Here is a look at each group.

Overview: The match between host Brazil and Croatia will open the World Cup on Thursday in Sao Paulo. The five-time champions are boosted by their boisterous fans and confident following the Confederations Cup victory last year, but Brazil will be looking to do better than it did at the past two World Cups, when it was eliminated in the quarterfinals. After barely qualifying, Mexico hopes to finally get past the second round in Brazil. Cameroon hasn't advanced past the group stage since 1990s. Croatia won't have forward Mario Mandzukic, who was red-carded in a decisive qualifier against Iceland.

Samuel Eto'o, Cameroon

After reconsidering a decision to retire, Eto'o will be carrying Cameroon's hopes of a surprising performance in Brazil. The striker, who will be 33 in Brazil, has been playing well with Chelsea.

Overview: Spain lost its opening match at the World Cup four years ago, but went on to beat the Netherlands 3-0 in the final. Those same two teams meet in one of the most anticipated opening matches. Spain has not lost a step as it vies to win a fourth major tournament in a row with a core squad likely playing its final World Cup. Netherlands is always a contender but was a flop at Euro 2012. The Dutch went unbeaten in World Cup qualifying. Chile is lurking, waiting to take advantage of any slip-up by Spain or the Netherlands. Australia has an inexperienced squad that is being groomed for the 2018 World Cup.

Robin van Persie, Netherlands

He must seize the opportunity after the Manchester United striker has scored only once at the past two major tournaments, the 2010 World Cup and Euro 2012.

Giorgos Karagounis, Greece

He remains motivator-in-chief at age 37, playing in eight qualifiers and both playoffs to reach a record 132 appearances for the national team.

Overview: With three former champions in Italy, England and Uruguay plus unpredictable Costa Rica, Group D is among the World Cup's toughest. As European Championship runner-up, Italy is the favorite. But Uruguay is the South American champion and few teams can match its strength at forward, with Luis Suarez and Edinson Cavani leading the way. England is hoping to carry over its form from an undefeated qualifying campaign, but it hasn't gotten past the quarterfinals in its past four World Cups and star player Wayne Rooney failed to score in the past two tournaments. Costa Rica has pulled off surprises before and conceded only seven goals in 10 matches of the final qualifying phase.

Mario Balotelli, Italy

Italy's intentions will likely depend on Balotelli, a talented forward whose mood swings often get him into trouble.

Antonio Valencia, Ecuador

The Manchester United winger is Ecuador's best-known player and could carry any hopes for an upset on his shoulders.

Overview: Barring a major upset at the World Cup, Argentina will finish at the top of Group F and let the other three teams compete for second place. Lionel Messi, Gonzalo Higuain, Angel Di Maria and Sergio Aguero — Argentina coach Alejandro Sabella has more attacking talent than he can fit into the lineup. By comparison, the defense doesn't look quite as impressive. Still, concerns about Argentina's vulnerability in the back shouldn't be exaggerated. The team conceded only 15 goals in 16 qualifying matches. Of the 32 countries in the tournament, only Bosnia is making its first World Cup appearance. Of the 30 goals the Iranians scored in qualifying, nine came on corner kicks or free kicks.

Lionel Messi, Argentina

The list of accomplishments for Messi, who will turn 27 during the Cup, is staggering. Suffice to say he is considered by many to be the best player in the world and is already in the conversation as one of the all-time greats.

Cristiano Ronaldo, Portugal

The winner of the Ballon d'Or as the best player in the world and a record scorer in the Champions League, Ronaldo gives Portugal a big weapon in the attack.

Overview: Group H might lack the appeal of teams such as Brazil and Germany and stars such as Messi and Ronaldo, but with Belgium players Vincent Kompany and Eden Hazard, and Russia coach Fabio Capello, the group shouldn't be disregarded. Capello got Russia to Brazil by winning a group which included Portugal, and that has given him enough confidence to keep his eye on the second round. Belgium might still be too young to reap the rewards of its talent, but there will be no waiting once they get to Brazil. Even if Group H seems easy, the rest of the way in the tournament will be anything but. After the group matches, the road will lead to the top teams from Group G, arguably the toughest of the tournament.

Eden Hazard, Belgium

The Chelsea playmaker has seen his stock rise during a standout season with Chelsea and an easy first-round group can do wonders for a player looking for recognition on the biggest stage.