At first glance, it's hard to tell what's special about the way the mentally disabled play soccer. The rules of the game are exactly the same, and the players' intellectual and learning disabilities are not easily visible. To qualify for the team, the players must have an IQ below 75 -- well below the overall average of 100.

The athletes have limited technical abilities and their grasp of the tactical twists of the game is only rudimentary, according to Willi Breuer, coach of the German team.

"The difficulties I have to deal with are mainly are of an organizational nature, because the players themselves just can't cope," Breuer said. "A big chunk of the work has to be spent on these things that are basic requirements to be able to work in a team. This is the big difference to working with soccer players without handicaps."

Players often miss their train to get to the training session on time or forget to bring money to pay for their bus tickets, Breuer said. Explaining new tactics can take several attempts because the players have difficulties grasping abstract information.

That also prevents the mentally disabled players from ever being able to compete with the professional players in the big leagues. That's why the International Sports Federation for Persons with Intellectual Disability (INAS-FID) decided to organize their own soccer world championship in the first place.

Home advantage for Germany

This is the competition's fourth year. England, the current world champions, are the odds-on favorite. But the German team is highly motivated and has a home advantage. The first game, between Germany and Japan, will be played on Tuesday.

"I am in high spirits and I am really looking forward to it," said Andreas Timm, who has been on the German team since the first championship. "I am very well prepared at the moment. We will see how far we will get. I would like to be in the final. But I also hope that this world cup will help integration between people with and without handicaps."

Ralf Kuckuck, the main organizer of the world cup, said the event is as an opportunity to build bridges not only between people from different countries but also between people with and without disabilities.

"We are organizing events where people can actually meet the athletes," Kuckuck said. "We want everyone to know that the fourth soccer world cup for disabled people is being held in Germany. And if I look how many people want to come to the games I think we have been successful. At this opening match in Duisburg we expect an audience of more than 16,000. It's the first time that there is so much interest in such a championship."

More than 140,000 people are expected to come to the matches. Tickets for the games are available for free, except for the Sept. 16 final, which costs a mere 5 euros ($6.38) to watch.