Saint Petersburg - French Open champion Jelena Ostapenko defeated Russian veteran Vera Zvonareva 7-6 (8/6), 6-3 to reach the St Petersburg Ladies Trophy quarter-finals on Wednesday.
World number six Ostapenko, who is the second seed, triumphed in one hour 38 minutes and will next face either Petra Kvitova of the Czech Republic or Romania's Irina-Camelia Begu.
"I have good memories about this event as I won the doubles title here last year," Ostapenko said. "Hopefully, this year I'll manage to perform well in the singles as well."
Zvonareva, 33, a former two-time runner-up at the majors, is on the comeback trail after taking two years out from the sport to marry and give birth to a daughter, Evelyn.
Russian qualifier Elena Rybakina, ranked a lowly 450 in the world, survived a match point to see off third seed Caroline Garcia of France 4-6, 7-6 (8/6), 7-6 (7/5) in two hours 26 minutes.
Garcia, ranked seventh in the world, was a set and 5-4 ahead in the second but her nerve failed her as she served for the match.
"It was very exciting to oppose such a high-ranked rival," said 18-year-old Rybakina said. "I'm really happy I managed to beat her. I just couldn't imagine I'd reach the last eight."