US teenager Coco Gauff on Thursday ousted Madrid winner Aryna Sabalenka in straight sets to advance to the quarter-finals of the Italian Open on Thursday. Belarus' Sabalenka, the world number four and seventh seed, fell 7-5, 6-3 to the 17-year-old Gauff, ranked 35, who reached her fourth quarter-final of the year. Six of the top ten WTA players have already exited the Foro Italico including second-seed Naomi Osaka of Japan, four-time Rome winner Serena Williams, Sofia Kenin and Petra Kvitova. Defending champion Simona Halep, the third seed, was forced out with a calf injury in her second round match. Gauff will play either world number one Ashleigh Barty of Australia or Russian Veronika Kudermetova for a place in her second semi-final this year after Adelaide. ea/pb