Mexico is considered to be one of the top medal contenders at the 2012 Summer Olympics in London, but they will face a stiff test right off the bat against South Korea on July 26 at Newcastle.

According to SI.com's Grant Wahl, South Korea will be the toughest test in Mexico's group. I'll admit that Wahl's statement was a bit of a shocker to me, as I've never associated South Korea as a soccer powerhouse. 

In addition to South Korea, Mexico will face Gabon and Switzerland. Switzerland is ranked No. 21 in the FIFA world rankings, while South Korea is ranked No. 28. Gabon is way down at No. 45, and Mexico shouldn't have any issues beating them.

So, why is Wahl singling out South Korea over Switzerland?

They enter the Olympics on a hot streak, having won three of their four matches so far in 2012 leading up to the Summer Games, their single loss coming against the best team in the world—Spain.

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The Korean Republic features some talented offensive players and Jung Sung-Ryong is a seasoned veteran goalkeeper who anchors their stout defense. 

Mexico will have their hands full keeping this hot team from scoring, and they'll have to work hard to get through their solid defense. 

This opening matchup will test Mexico's mettle right off the bat, and it will be interesting to see how they respond to the challenge.