US Open champion Coco Gauff swept into the Australian Open second round on Monday but Wimbledon winner Marketa Vondrousova was sent packing as Naomi Osaka readied for her Grand Slam comeback."I have a much more positive mindset and a much more grateful mindset," four-time Grand Slam champion Osaka said of returning to Melbourne, the scene of her title-winning exploits in 2019 and 2021.