Bertens easily saw off Belgian qualifier Ysaline Bonaventure 6-4, 6-2 in their second-round match, while Pavlyuchenkova saved five of six break points on her way to a 6-4, 6-4 upset of former French Open champion Jelena Ostapenko.
The eighth-ranked Bertens lost to Pavlyuchenkova two weeks ago in the second round of the Australian Open 3-6, 6-3, 6-3. Pavlyuchenkova went all the way to the quarterfinals on that occasion before losing to Danielle Collins.
Bertens leads 3-2 in career matches against Pavlyuchenkova, though the Russian has won their last two meetings. Thursday's win over Bonaventure was Bertens' first match since her Australian Open loss thanks to a bye in the first round in St. Petersburg.
Earlier Thursday, Aryna Sabalenka recovered from a second-set slipup to reach the quarterfinals, beating Alison van Uytvanck 6-1, 6-4. In her first match since reaching a career-high ranking of No. 10 on Monday, the Belarusian trailed 3-1 in the second before winning four games in a row.
Sabalenka, who had a first-round bye, will next face Ekaterina Alexandrova, who beat qualifier Tereza Martincova 7-5, 6-2. Sabalenka defeated Alexandrova 6-3, 6-3 this month on her way to winning the Shenzhen Open title.
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