Six years ago, Naomi Osaka made history at the 2018 US Open but Serena Williams’ furious tirade took the headlines. Williams had made a miraculous return to tennis after the birth of her daughter Olympia, which left her with serious health problems. Having spent six weeks bed-ridden, the 23-Grand Slam winner suffered life-threatening blood clots but fought back to reach the US Open final against all the odds. Standing in her way was Osaka, a relative unknown before the US Open got underway that year, beginning the year ranked 68th in the world. Aged 20, Osaka had to pinch herself as she prepar…