“The moral of the story? You never know when I could be coming to a tennis court near you!” That was how Serena Williams reflected upon a random encounter as she crashed a tennis match between two strangers while out on a walk. The world number one and arguably the greatest player of all time was taking a stroll around Dolores Park in San Francisco's Mission District when she thought of “asking these guys” if she could have a hit with them, “just to see their reaction”. Well, it's fair to say that they were pretty stunned and delighted. The 23-time Grand Slam champion did not have trainers on, but proceeded to lace up her boots regardless, telling fans on the social-media platform snapchat, “don't do this at home”. Her fiance, Alexis Ohanian, filmed one of the men playing a very short rally with the Australian Open winner heard saying “Don't get tight!” to her bewildered opponent.