Former US Open champion Raducanu swept the first set in 22 minutes but faltered in the second and had her left ankle examined during a medical time-out, before leaving the court in tears after being unable to complete the first point of the decider.The Australian Open begins on January 16.Earlier, Coco Gauff beat fellow American Sofia Kenin 6-4, 6-4 to set up a quarter-final match against China's Zhu Lin, who outlasted Venus Williams 3-6, 6-2, 7-5 in a rain-hit match that ran two hours and 23 minutes.