BERLIN (AFP) - Kenya's defending champion Janeth Jepkosgei's hopes of retaining her 800 metres title came to a disastrous end in the first round here at the World Athletics Championships on Sunday. The 26-year-old silver medalist in the 2008 Olympics went crashing to the track on the final bend as young South African sensation Caster Semanya tried to move to the outside. However, their legs became entangled and it was the Kenyan who came off worse as she fell and was trod on by several of the other runners, while Semanya also almost came down. The 18-year-old South African, however, regained her composure and ended up winning the heat with Jepkosgei coming in a forlorn last. Semenya, who produced two amazing performances in South Africa earlier this year to take the South African junior 800m and 1500m titles, indicated, however, that she was no certainty to be able to be fit enough for the semi-finals as she too had come out of the clash in bad shape. "I don't know what happened (about the incident that led to the fall)," she said. "I didn't see anything because I was looking forwards. "I just saw the Kenyan fall and I tried to jump over her. However, I twisted my ankle in doing so. At the moment I have no feeling in my ankle. I need to see the physio to check my leg. If it's not good I'll quit." Jepkosgei had been heavily favoured to avenge her defeat in last year's Olympics by teenage compatriot Pamela Jelimo, whom she had advised to move up to that distance. The 19-year-old Jelimo later had no such trouble in her first round heat as she sprinted clear of her rivals to firmly place her as favourite to add the world crown to her Olympic title. However, like Semenya, Jelimo was not feeling physically at her best either. "I tried to run but it was as if there was something there (she showed her ankle where she had got spiked). "I have some pressure being the only Kenyan left, but I know it will be okay. "The field is tough, it's going to be tactical." The final heat also suggested she may not have it all her own way. Cuba's 2005 world champion Zulia Calatayud won impressively from Morocco's Hasna Benhassi, who will be looking to turn her impressive array of two minor medals at the Olympics and another two at the world championships into gold finally.