Beijing (AFP) - Ukrainian Elina Svitolina scored her second win this year over a world No. 1, ousting Angelique Kerber in the round of 16 in Beijing on Thursday.
Nineteenth-ranked Svitolina won 6-3, 7-5.
The 22-year-old left Serena Williams in tears at the Rio de Janeiro Olympics in August, denying the former top-ranked player a fifth Olympic gold medal with a straight set win.
Kerber, who had her right thigh taped, had a break lead in each set but appeared glued to the baseline during the match and was unable to take control.
"I know that I have to move very well when I play my game, and I couldn't play my game like I play," Kerber told reporters after the match.
The German still plans to play in Hong Kong next week as she chases points to end the year at No. 1 - but her right leg may alter her plans.
Briton Johanna Konta secured her first ever win over US Open finalist Karolina Pliskova in a three set tie break, 6-1, 3-6, 7-6 (7-2).
With a victory over the sixth-ranked Czech, Konta - currently at No. 14 - moves closer to breaking into the top 10 for the first time.
The win also moves the 25-year-old into 10th position in the race for the WTA Finals in Singapore. Eight singles players will feature at the prestigious season-ender at the Singapore Indoor Stadium.