Usain Bolt was left ruing a disastrous start as his failure to fire saw American arch-rival Justin Gatlin poop what was supposed to be a party in his final 100m race at the world championships on Saturday. "My start is killing me," said Bolt, who battled back up through the field to claim bronze behind Gatlin and silver medallist Christian Coleman. "Normally it gets better during the rounds, but it didn't come together. And that is what killed me. I felt it was there."