Osaka won both her matches in straight-sets on Thursday.
World number one Naomi Osaka made it safely through to the quarter-finals of the Italian Open but Simona Halep and Petra Kvitova were surprise casualties.
Osaka, of Japan, won both her matches in straight-sets on Thursday, after Wednesday's rain forced the players to play two matches in a day.
She beat Dominika Cibulkova of Slovakia 6-3 6-3 before sinking Romanian Mihaela Buzarnescu by the same scoreline.
Osaka will face Kiki Bertens of Holland, who needed three sets to get past both Amercan Amanda Anisimova and Spain's Carla Suarez Navarro.
French Open champion Halep crashed out in three sets in the second round to Czech teenager Marketa Vondrousova, a defeat which means Osaka is guaranteed to be top ranked at Roland Garros.
Kvitova, the second seed, dropped just one game in beating Yulia Putintseva but then ran into in-form Maria Sakkari of Greece in round three.
The Czech was 4-0 down in the deciding set when she retired injured.
Britain's Johanna Konta reached her first big clay-court quarter-final with back-to-back victories over former grand slam champions Sloane Stephens and Venus Williams.
Her 6-7 (3) 6-4 6-1 victory over French Open runner-up Stephens in the second round was arguably the most impressive of her career on clay.
Williams had her right knee strapped and for the first two games she could hardly move or serve.
She improved after that but never looked capable of making a match of it as long as Konta kept her head, which she did to win 6-2 6-4.
Victoria Azarenka of Belarus is also through after former Wimbledon champion Garbine Muguruza found two matches in a day too much, retiring early in the second set.