The United States will have a presence at today's semifinal World Cup match between Brazil and Germany. It won't be the U.S. National Team on the field, but American referee Mark Geiger. FIFA selected Geiger to be on the officiating crew of the high-stakes match. It's the first time a U.S. referee has been used this late in a World Cup.

Earlier, Geiger made history when he officiated the knockout game between France and Nigeria on June 30. Before that, American referees had never been used beyond group play of the World Cup. Now, Geiger is making history again with his selection as the fourth official. He will handle administrative duties during the 4 p.m. ET match, including player substitutions. He'll also be the one who hoists the electronic board at midfield when players are entering or exiting the field.

Geiger has already had a strong World Cup despite some controversy during that France-Nigeria game. He was the center referee for three matches, was the fourth official in another, and now is in the semifinal.

The last time a U.S. referee was even used at the World Cup was in 2002. As a referee, just being selected to officiate at this level is a tremendous honor. Geiger was one of just 25 referees brought to Brazil. But one bad call in the first game, and your World Cup career can end. During games, FIFA assessors study every move, every call the referee makes (or doesn't), and give him a grade at the end of the game. If the score is not high enough, the referee is finished.

In announcing Geiger's selection and that of the other referees for the final games, FIFA said:

"The committee defined the list after careful monitoring of all referees and assistant referees on a daily basis together with the technical staff. In line with how designations have been made throughout the tournament, quality was the main criteria, while physical, medical and technical aspects were also taken into consideration."

Geiger is 39 and lives in Beachwood, N.J. Until last year, he was a high school math teacher. Like his success on the field, he was just as good in the classroom. In 2010 he won a prestigious Presidential Award for Excellence in Mathematics and Science Teaching. But he gave up his job to focus on being a full-time professional referee with hopes to make the World Cup. He got his start as a 13-year-old (to pocket some extra money) and moved up the ranks as a U.S. Soccer referee and eventually began officiating Major League Soccer games in 2004. He was the MLS Referee of the Year in 2011. A year later, he officiated during the London Olympics.

In an interview with the New York Daily News before the World Cup, Geiger said he was ready for the intense pressure of getting every call right.

"There's going to be debate on whether calls are correct or not. You do your best to do your homework, know who the players are and know which management technique is going to work with each of them."

For now, Geiger says he still loves life as a professional soccer referee. But he hasn't ruled out a return to the classroom at some point.

"I do miss the kids, I do miss the classroom. I can always go back in 10 years or so when the refereeing is done."

But Geiger's job at the World Cup isn't done. He'll have a front row seat to what could be one of the best games of this year's tournament so far.

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