In a chaotic first weekend at the World Track and Field Championships in South Korea, Oscar Pistorius and Usain Bolt, perhaps the sport's two most popular runners, both struggled to find the finish line in their respective events. Pistorius, an amputee who runs with carbon-fiber prosthetic legs below the knee, qualified for the semi-final of the 400 meters with a strong 45.39 first-round run on Saturday. But on Monday afternoon in Daegu, he finished last in his semi-final heat and did not qualify for Tuesday's final. "I would have liked to perform better tonight,'' he said. Bolt, the world record holder at both 100 and 200 meters, had no trouble getting to the starting line of the 100, but was disqualified after moving too early out of the blocks in Sunday's final. He was caught under a new and controversial "one and done" false-start rule, which the IAAF will likely review before the London Olympics next year. Bolt's Jamaican teammate Johan Blake won the race in 9.91 seconds, with American Walter Dix second. Bolt and Pistorius will each have an opportunity for redemption later this week. Pistorius is expected to lead off South Africa's 4 by 400-meter relay on Wednesday, and Bolt will run the 200 meters on Friday. "I know that I am now in good shape," Bolt said Monday.