World number eight Kiki Bertens is now in double figures for WTA titles after she once again proved to be a cut above in St Petersburg.
Illness forced Petra Kvitova to withdraw at the St Petersburg Ladies Trophy, while defending champion Kiki Bertens reached the semi-finals.
All four semi-finalists in the Tianjin Open are unseeded after Magda Linette, Yulia Putintseva and Dayana Yastremska crashed out.
Tianjin Open favourite Wang Qiang was no match for Heather Watson as the Briton secured a first win over a top-30 player since 2017.
Madga Linette offered little resistance as Karolina Muchova cruised to a 6-1 6-1 triumph in the final of the Korea Open on Sunday.
Samantha Stosur's hopes of ending her two-year wait for a WTA Tour title were ended by Sofia Kenin on Saturday.
Madga Linette, who lost to Naomi Osaka at the US Open, put in an impressive display as she progressed to the quarters at the Jiangxi Open.
Veronika Kudermetova was a straight-sets winner over Varvara Lepchenko at the Japan Women's Open on Monday.
Magda Linette was one of the form players at the US Open but she could not stop Naomi Osaka reaching round three.
Camila Giorgi was in control of the deciding set, but ultimately fell to a late surge from first-time WTA Tour winner Magda Linette.