After four years of dominating heavyweight judo and mulling over the one that got away, Teddy Riner will face his moment of truth when the Olympic judo competition begins on Saturday. The five-time world champion has only lost one major international fight since the last Olympics and even that was a contentious judges' decision against Daiki Kamikawa in the Japanese's home city of Tokyo. But despite his otherwise total domination of his rivals, Riner's Olympic failure in Beijing still burns inside him. Four years ago he was narrowly defeated on a penalty score in the semi-finals by Uzbek Abdullo Tangriev and he had to settle for bronze. The giant Frenchman is candid about how important Olympic success is to him and describes it as a dream. Yet whereas he was a 19-year-old upstart, albeit already world champion, in 2008, he is now one of the clearest favourites ever in the sport. Should he fail to win the gold medal, it would be a major shock. Even world number two and the man Riner beat in last year's World Championship final Andreas Toelzer of Germany admits it would be a tall order for him to topple the two-metre Frenchman. "I don't prepare for Riner, I have so many fights before Riner and if I get to the final and can get to fight him it would already be a big win for me," he said. "And afterwards, maybe I can beat him, I don't know. He's one of the biggest stars in judo but I beat him one time and maybe I can do it a second time." Last year at the World Championships, Toelzer claimed to have a secret weapon to beat the Frenchman but he seemingly failed to employ it as he was beaten by the maximum ippon (a technical knock-out) score. He says he has a different secret weapon this time but added: "You'll have to wait to see it on the mat." Perhaps the biggest threat to Riner will come from Kamikawa as he is the only man to have beaten the Guadeloupe-born star in the last four years and they are due to meet in the semi-finals. Conversely, though, it is the French who will likely prove Japan's toughest competition as the country that gave judo to the world looks to continue its dominaton of the sport. France has three world champions in the women's divisions in Lucie Decosse at under-70kg, Gevrise Emane at under-63kg and Audrey Tcheumeo at under-78kg. They will all provide stern opposition to the likes of Yoshie Ueno, the world number one at under-63kg, and her Japanese team-mates Akari Ogata and Haruka Tachimoto. Greece's Ilias Iliadis, world champion at under-90kg, will be expected to light up the competition as he goes in search of his second Olympic gold following his victory at under-81kg eight years ago. He is one of the most spectacular fighters in the world but has some tough opposition in Georgia's Varlam Liparteliani, Japan's Masashi Nishiyama and Tiago Camilo of Brazil. Two Olympic champions will face off in the men's under-81kg division with title-holder Ole Bischof of Germany challenged by Azerbaijan's Elnur Mammadli, winner at under-73kg in Beijing, as well as world champion Leandro Guilheiro of Brazil. After Riner the biggest single favourite is double under-60kg world champion Rishod Sobirov of Uzbekistan, a bronze medallist four years ago. Similarly, reigning women's heavyweight champion Tong Wen of China is expected to retain her title, although Japan's Mika Sugimoto could upset her. Japan should dominate the women's lightweight divisions with Tomoko Fukumi (-48kg), Misato Nakamura (-52kg) and Kaori Matsumoto (-57kg). China will be looking to another reigning champion in Yang Xiuli to bring home another gold at under-78kg.