Anastasia Pavlyuchenkova has beaten fourth-seeded Agnieszka Radwanska 6-4 6-7 (7-4) 6-1 to advance to the Rogers Cup quarter-finals.
Pavlyuchenkova, the Russian seeded 16th, let two match points slip away while leading 5-4 in the second set and then lost the game on a double fault.
She rebounded in the third set to extend her longest run at the hardcourt event.
“I think I’m still recovering from the second set,” Pavlyuchenkova said.
“Basically, I thought I had the match in my pocket and lost it, so I’m happy with the mental side.”
Radwanska, from Poland, won the Rogers Cup the last time it was held in Montreal in 2014.
Pavlyuchenkova will face the Venus Williams-Madison Keys winner in the quarter-finals.
Second-seeded Angelique Kerber of Germany also needed three sets to advance, beating Ukraine’s Elina Svitolina 1-6 7-6 (7-2) 6-4. Kerber will face Russia’s Daria Kasatkina, a 7-5 6-3 winner over seventh-seeded Roberta Vinci of Italy.
Fifth-seeded Simona Halep of Romania, a finalist last year in Toronto, beat 14th-seeded Karolina Pliskova of the Czech Republic 6-3 6-3.
“I knew that it’s going to be tough because I don’t get rhythm from her,” Halep said.
“You never know what to expect for the next point, so there’s a bit of tension.
“I just had to stay patient for every ball and to keep fighting because I knew that if I stay there for every ball, she can miss more than me.”
Halep will face ninth-seeded Svetlana Kuznetsova, a 7-6 (7-2), 6-3 winner over 12th-seeded Petra Kvitova of the Czech Republic.