Romania's Sorana Cirstea upset fourth-seeded Karolina Pliskova 6-1, 7-5 on Thursday to earn a spot in the quarterfinals of the China Open in Beijing.
Cirstea, ranked 44th in the world, knocked out her fourth-ranked Czech opponent in 83 minutes during the third-round match.
Pliskova was hampered by six double faults. Though she leads the WTA Tour in aces this season, she managed just two against Cirstea.
The Romanian was particularly clutch on key points, converting six of her seven break points and saving eight of the 11 break points on her own serve.
Cirstea's next opponent will be ninth-seeded Jelena Ostapenko. The Latvian advanced when China's Shuai Peng was forced to retire due to a leg injury while trailing 3-0 in the first set. The only career meeting between Ostapenko and Cirstea came in the U.S. Open this summer, a second-round Ostapenko victory.
In other early action Thursday in Beijing, Caroline Garcia beat Alize Cornet 6-2, 6-1 in an all-French third-round match. Garcia had six double faults to one for Cornet, but Garcia's superior success on first serves (71 percent to 45 percent for Cornet) proved critical.
Garcia advances to a quarterfinal match against either third-seeded Elina Svitolina of Ukraine or unseeded Elena Vesnina of Russia.