Caroline Wozniacki had to come from a set down to see off Varvara Lepchenko in the third round of the Rogers Cup in Montreal.
The seventh seed lost the opening set 4-6 but got herself back in the match with a 6-3 win in the second.
The Dane sealed her place in the last eight by taking the deciding set 6-4.
Wozniacki will now face Canada's Aleksandra Wozniack for a semi-final berth.