MELBOURNE: World 100m freestyle champion Mollie O’Callaghan edged Olympic gold medallist Emma McKeon by a fingertip in the year’s fastest time Saturday ahead of a blockbuster world championships next month. It was the second time in as many races that the Australian teenager had taken down her more illustrious teammate, having also beaten her in April. She touched at the Australian trials in Melbourne in 52.48 seconds, with McKeon hitting the wall a fraction behind in 52.52. Along with Hong Kong’s Siobhan Haughey, they will head into the Fukuoka world championships in Japan as hot medal favourites. “I kind of just had to trust myself and believe that I could touch that wall first,” said O’Callaghan, who upset Olympic champion Ariarne Titmus to win the 200m earlier in the week. “The depth here is incredible, it’s so close in each race. I just came into this to just try to get top or relay,” added the 19-year-old. All the top five – also including Shayna Jack, Meg Harris and Maddie Wilson – were under the qualifying time. It puts them in contention for a place on Australia’s all-conquering 4x100m relay team, which holds not just the world record but nine of the top 10 times in history.