Slovakian top seed Dominika Cibulkova beat Zarina Diyas of Kazakhstan 4-6 6-2 6-4 to reach the semi-finals of the WTA BMW Malaysian Open.
The world No 10 saved an incredible 20 break points on her way to a gruelling two-hour victory over her sixth-seeded opponent.
Cibulkova will play third seed Karolina Pliskova of the Czech Republic in Saturday's semis, after she saw off Turkey's Cagla Buyukakcay 6-4 6-4.
In the other semi-final, second seed Shuai Zhang of China will face Donna Vekic of Croatia.
The 45th-ranked Zhang was also made to battle as she fought off 10 break points to beat Magda Linette of Poland 6-2 2-6 6-1.
Vekic, who is yet to win a WTA Tour title, sent down 10 aces in her 6-4 7-5 win over fourth-seeded Austrian Patricia Mayr-Achleitner.