NEW YORK: Serena Williams battled into a US Open semi-final showdown with Victoria Azarenka on Wednesday as top men’s seeds Dominic Thiem and Daniil Medvedev booked their spots in the last four.Williams, seeded third, came from a set down to overcome unseeded Bulgarian Tsvetana Pironkova and keep alive her bid for a 24th singles Grand Slam title at Flushing Meadows.Later, Azarenka blew away Belgium’s Elise Mertens as she continues her hunt for a first Grand Slam title in seven...