Here is a crash course on the 2014 World Cup and how the tournament works.

Lionel Messi scored his first goal in a World Cup since 2006 to lead Argentina to a tournament-opening win over Bosnia and Herzegovina.

The best player in the world has not had the best track record in World Cups, but leading La Albiceleste in its rival country, Messi showed his brilliance as he dodged through several opponents to finish a left-footed shot off the post and into the net. 

The win gives Argentina sure control in a relatively weak group, with Iran and Nigeria next. 

Bosnia, meanwhile, will be happy with its performance against Argentina and remains a favorite to advance out of the group.

Watch the full highlights here

In other performances on Sunday...

* Switzerland added to the drama of the World Cup with a last-gasp winner over Ecuador in the dying moments of injury time. Haris Seferovic scored at the near post in the 93rd minute on the back-end of a counter attack that started with a near-chance for Ecuador. The referee's decision to play on at the start of the counter was crucial, and Switzerland vaulted itself to three points. Watch the game highlights.

* France downed Honduras, 3-0, to take control of Group E in its opener. It started off as an ugly game, with Honduras resorting to a more physical style of play to try to keep pace with France. Paul Pogba was lucky not to be red-carded, but Wilson Palacios was ejected as France advanced on a pair of goals from Karim Benzema and a third goal that was due to Benzema's efforts. This game most notably included the first use of goal line technology, as the second goal came when Benzema's shot hit off the inside of the post and then was pushed in by just a few inches off the hand of goalkeeper Noel Valladares. Watch the game highlights.

What's on tap on Monday...

12 p.m. ESPN - Germany vs. Portugal - Another sexy match-up in the group stages, two of the top teams in the world face off to open Group G play. Cristiano Ronaldo says he is 100-percent fit to face off against Germany, and the Germans will look to utilize their multi-faceted attack behind players like Bastian Schweinsteiger, Mesut Ozil, Mario Gotze and Thomas Muller

Keep an eye on: Germany's Gotze, an incredibly talented midfielder who has been heralded as "the German Messi," by Franz Beckenbauer, he could be the key to Germany's World Cup hopes. Gotze had 10 goals and 10 assists in 20 Bundesliga starts for Bayern Munich this year.

3 p.m. ESPN - Iran vs. Nigeria - A decidedly less sexy match-up, U.S. fans got a chance to see Nigeria up close in the Americans' win over the Super Eagles in Jacksonville. Iran finished atop its group in Asian qualification, and will be led by Fulham's Ashkan Dejagah.

Keep an eye on: Nigeria's John Obi Mikel, the bruising midfielder who plays for Chelsea in the premier league. He'll be the best player on the field for both teams, and will be a box-to-box player for Nigeria.

6 p.m. ESPN - Ghana vs. United States - We'll go more in depth on this game on the blog later today. The U.S. look at this game as a must-win. Three points puts the Americans in a strong position going into their second game of the tournament against Portugal. Ghana holds a mental edge, however, having knocked the U.S. out of the last two World Cups. 

Keep an eye on: U.S. defender Fabian Johnson, the right back for the U.S. is a left-footed player who has proven to be a crucial cog to their attacking hopes in this inverted role as he charges up the sideline with an ability to cut in and create chances. 

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