World No. 1 and defending champion Iga Swiatek crashed out of the US Open on September 4 with a 6-3, 3-6, 6-1 loss to Jelena Ostapenko.
With this victory, Ostapenko leads 5-0 in their head-to-head meetings.
The Latvian will play her first USO quarterfinal on September 5 verus sixth seed Coco Gauff.
Gauff edged past former world no. 1 Caroline Wozniakci in a three-set thriller earlier at the Arthur Ashe stadium to make a consecutive quarterfinal at Flushing Meadows.
The 19-year-old is the first American teenager since Serena Williams in 2000 to play in back-to-back quarters.
Meanwhile, in the men's draw, 23-time Grand Slam winner Novak Djokovic eased past Borna Gojo in straight sets 6-2, 7-5, 6-4 to set up a quarterfinal clash with American Taylor Fritz.
If Fritz can manage to defeat Djokovic, he will have a shot at the title, which has evaded American male players since Andy Roddick's 2003 triumph.
For the first time since 2005, three American men are through to the last eight in New York.
Ben Shelton took 4 sets to defeat compatriot Tommy Paul while Frances Tiafoe made little work of unseeded Rinky Hijikata.