Australia's Nick Kyrgios sent defending champion Daniil Medvedev tumbling out of the US Open on Sunday as US teenager Coco Gauff reached the quarter-finals for the first time. The notoriously temperamental 23rd-seeded Kyrgios produced some scintillating shot-making on his way to a superb 7-6 (13/11), 3-6, 6-3, 6-2 win over the world number one from Russia. Kyrgios, who was beaten by Novak Djokovic in the Wimbledon final in July, showed ...