Kasatkina was beaten in just 78 minutes by Zheng Shuang, who dropped just three sets in her 6-1 6-2 win over world No. 8.
Zheng Zhi, who beat world No. 12 Jelena Ostapenko earlier this week, used her serve and volley method expertly throughout as the 20-year-old secured her third career top-10 finish Victory, and a third trip to the semi-finals of the Tournament – the final.
Another Russian stood ahead of Zheng He’s place in the final after No. 8 seed Lyudmila Samsonova beat compatriot Veronica Kudermetova 6-3 6-3.
Bencic found his form in a tough first set against qualifier Shelby Rodgers, who finished 7-6 (7-5) 6-2.
No. 2 seed Bencic will face Beatrice Haddad Maya in the semifinals after the Brazilian beat Yulia Putintseva 3-6 6-3 6 in less than 24 hours. -2 over Wimbledon champion and Australian Open runner-up Elena Rybakina. Marathon meets in three hours.
Meanwhile, first seed Maria Sakkari secured her place in the semi-finals by beating Donna Vekic 6-3 7-6 (10-8) in straight sets at the Linz Open.
The Greek next faces Petra Martic, while Anastasia Potapova faces unseeded Marchita Vondrosova in the other semi-final.