Elena Rybakina's Kazakhstan dumped defending champions Germany out of the United Cup on Wednesday with Alexander Zverev sidelined by an arm injury barely a week away from the Australian Open, while top seeds USA beat China to reach the semi-finals. In Sydney, women's world number two Iga Swiatek led Poland into the last eight by winning a rematch of her 2023 French Open final against the Czech Republic's Karolina Muchova. Britain also progressed to the quarter-finals with Katie Boulter's dominant 6-2, 6-1 victory over Australia's Olivia Gadecki enough to guarantee they won their group.