Two men face each other, knowing that a single kick is about to decide their teams' fate as more than 700 million viewers watch: it must be a World Cup penalty shootout.

There is more than a 50 percent chance that the winners of the World Cup in South Africa, which kicks off on June 11, will have to survive a penalty shootout en route.

Some of the world's top sportsmen will inevitably buckle under the pressure, consigning millions of fans to despair and a lifetime of muttering "what if...?"

Derided as a lottery by critics, the penalty shootout is unsurpassed as the ultimate test of nerve to decide tied games. Despite its flaws, it makes compulsive viewing.

The split-second moment can make a player a hero, or forever scar an otherwise unblemished career.

"It affected me for years," said Roberto Baggio, the Italian forward who was one of the best players of the 1994 tournament until he missed in a shootout defeat to Brazil in the final.

"It was the worst moment of my career. I still dream about it. If I could erase a moment it would be that one."

England's Stuart Pearce shared that sentiment after missing in a 1990 semi-final defeat to Germany.

"My world collapsed. The walk back to the centre circle was a nightmare as the first rush of tears pricked my eyes," Pearce said years later.

Four of the last five winners of the world's biggest sports event have had to come through a shootout test of nerve during one of their four knockout games, including Italy and Brazil in the final games of 2006 and 1994.

Since penalties were introduced in 1982, to decide matches that remained drawn after extra time, there have been 20 shootouts in seven tournaments.

Five players from each side take a kick and if the scores are level a "sudden-death" process starts.

Fifty-six, or 30 percent, of the 186 spot kicks have been missed.

The Swiss, Mexicans, Romanians and Dutchmen have yet to win a shootout, while this year's favourites, Spain, may need to improve their record of one win from three.

"It may not be wholly representative of the game but it's a test of skill under pressure and some countries have proved good at it," said Matt Pain, part of Loughborough University's football psychology research unit in England.

"It's clearly not a lottery because the statistics show how many Germany have scored and how many England and the Netherlands score."

Coaches going to South Africa will spend much time on research, trying to improve their chances, backed up by sports science and psychology experts who have spent hundreds of hours studying the art.

Sixty percent of shootouts are won by the team going first, so the captain who wins the coin toss can grab a clear advantage before a ball is kicked.

From there, it gets more technical, but experts say the key is controlling the pressure.

"Penalty shootouts are really a psychological game," said Geir Jordet, associate professor at the Norwegian School of Sport Science in Oslo who has studied shootouts extensively.

"It's not so much about technique or skill, it's about players choking. Shootouts are not decided by great shots or spectacular penalties. They are decided by the one, two or three players who fail because the pressure gets to them."

Jordet's research has highlighted several reasons why some players and countries fail.

English, Spanish, Italian and Dutch players, for example, rank high in terms of "star" status, having enjoyed club success and great popularity at home, which piles on more pressure.

His research has shown English players take kicks quicker than players from any other country, reflecting their desire to get them over as soon as possible.

Germany's clinical approach -- the team are said to have a database of more than 10,000 penalties and goalkeeper Jens Lehmann was seen studying a crib sheet tucked into his sock during a quarter-final shootout four years ago -- is being copied by others anxious to know which way opposition goalkeepers tend to dive and which way players prefer to aim.

In the run-up to this year's tournament, all the top teams will practise their technique from the penalty spot.

"You can't replicate the exact emotions you're going to have but, as Tiger Woods does with putting, you can practise a skill to give you more chance when the pressure is on," said Loughborough University's Pain.

The English, Swiss, Dutch and Mexicans can at least hope that if tested this time they can reverse their fortunes.

Baggio may have helped to inspire that victory. After his miss in 1994 he stepped up again four years later to score, albeit in another defeat against France.

"I've never run away from my responsibilities," Baggio said. "Only those who have the courage to take a penalty miss them."

The 2010 soccer World Cup kicks off in South Africa on June 11 and many matches could be decided by penalty shootouts.

In the knock-out phase, which starts on June 26 and ends with the final on July 11, games which are drawn after extra time will be decided by penalty shootouts. Five players from each side take a kick, and then, if the scores are level, a "sudden-death" process starts.

Since the format was introduced in 1982 there have been 20 shootouts in seven tournaments.