PARIS - France's Olympic judo champion Teddy Riner could have to undergo surgery on a painful shoulder injury next week, his coach told AFP on Tuesday. Franck Chambily said Riner had a small piece of cartilage that was pushing on a tendon at the top of his left shoulder and causing the athlete pain. "It's better to remove it," said Chambily, adding that a non-surgical technique would be tried first before resorting to surgery next week which could sideline the athlete for up to six weeks. Riner pulled out of the Paris Grand Slam last weekend because of the problem. The eight-time world champion will be bidding to defend his +100kg Olympic title in Rio de Janeiro in August. After a winter break, Riner had kick-started training in early January before attacking an Olympic season.