Johanna Konta of Britain upset top-seeded Simona Halep 6-3, 3-6, 7-5 to advance to the quarterfinals of the Wuhan Open.
Konta, who came into the Wuhan tournament 66th in the rankings, stormed back to win the last six games of the third set and will face Venus Williams in the quarter-finals.
"It was two hours and 17 minutes of very, very tough tennis for me," Konta said.
"Simona really played some unbelievable tennis in parts - she may not be feeling her best - but I'm just really happy I was able to take a few of the chances I created."
Meanwhile, Williams hit five aces and saved three of four break points to see off Carla Suarez Navarro of Spain 6-3, 6-4.
"I had some luck because I think she missed a few shots today, and it gave me some openings," Williams said.
Williams and Konta will be facing each other for the first time.
In the day's first upset, Roberta Vinci beat defending champion and third-seeded Petra Kvitova 7-6 (3), 6-2.
The 15th-seeded Italian saved five of seven break points and next faces eighth-seeded Karolina Pliskova, who defeated Elina Svitolina 2-6, 6-4, 6-4.
Also, fifth-seeded Garbine Muguruza rallied to beat ninth-seeded Ana Ivanovic 4-6, 6-1, 6-0.
Muguruza will next face Anna Karolina Schmiedlova who beat Kristina Mladenovic 6-4, 6-2.
6-Angelique Kerber (Germany) beat Camila Giorgi (Italy) 6-2 6-4
Johanna Konta (Britain) beat 1-Simona Halep (Romania) 6-3 3-6 7-5
8-Karolina Pliskova (Czech Republic) beat 12-Elina Svitolina (Ukraine) 2-6 6-4 6-4
Anna Karolina Schmiedlova (Slovakia) beat Kristina Mladenovic (France) 6-4 6-2
15-Roberta Vinci (Italy) beat 3-Petra Kvitova (Czech Republic) 7-6(3) 6-2
Venus Williams (U.S.) beat 7-Carla Suarez Navarro (Spain) 6-3 6-4
5-Garbine Muguruza Blanco (Spain) beat 9-Ana Ivanovic (Serbia) 4-6 6-1 6-0