DAEGU (AFP) - World heptathlon champion Jessica Ennis Tuesday left herself an all-but-impossible task to defend her crown in the final 800m event after a disastrous javelin effort. Russian Tatyana Chernova, on 5,887 points, pulled out top performances in the long jump (6.61m) and javelin (52.95m) to leapfrog Ennis (5754 pts), the Briton only managing a best of 39.95m in the javelin, into top spot. Going into the evenings 800m, in which Chernova has a personal best 2sec quicker than that of Ennis, the Russian has a 9sec cushion and only a catastrophe will stop her claiming gold in the gruelling two-day, multi-discipline event. Germanys Jennifer Oeser (5,613) and American Hyleas Fountain (5,611) are locked in a battle for the bronze medal. Also Tuesday, Kenyan distance runners admitted after heats in the mens 1500m and womens 5000m that team tactics would be employed to add to the incredible opening day cleansweep of all medals on offer in the womens 10,000m and marathon. In the 1500m, two-time world indoor silver medallist Daniel Komen was fastest in qualifying for Thursdays semi-finals, where he will be joined by team-mates Silas Kiplagat, the Commonwealth champion, and current Olympic champion Asbel Kiprop. All of us Kenyans are teaming up for something special, warned Komen. Kiplagat added: After the semi-finals, I will sit down with my team-mates and come out with a tactical way of winning the title. One of their toughest challenges will come from defending champion Yusuf Kamel of Bahrain, formerly Kenyan Gregory Konchellah, whose father Billy was a two-time world 800m champion for the country of his birth. To be honest, I did not feel very comfortable, said Kamel, who also won bronze in the 800m at the Berlin worlds in 2009.