Karolina Pliskova defeated Czech compatriot Petra Kvitova in straight sets to secure her place in the semi-finals of the WTA Finals in Singapore.
World number eight Pliskova, 26, won 6-3 6-4 for her first victory over Kvitova, 28, in four attempts.
It is the second successive year former world number one Pliskova has reached the semi-finals at the season-ending tournament.
“I cannot be more happy right now,” said seventh seed Pliskova.
“It was a good match and she’s a great player. She has always beaten me in the past but I knew I had a chance as I have been playing well.”