Krystyna Pliskova of the Czech Republic came from a set down to upset 16th-seeded Roberta Vinci of Italy 3-6, 7-5, 6-3 at the Dubai Tennis Championships on Sunday.
The 58th-ranked Pliskova, who played under the watchful eye of her twin sister, second-seeded Karolina Pliskova, was facing defeat as Vinci served for the match at 6-3, 5-4.
But Pliskova won the next four games, and then broke Vinci's serve in the sixth game of the third set to secure the victory.
"I was trying to fight the whole match, but sometimes you play bad games," Pliskova said. "I tried to be more aggressive and she made some mistakes."
Tunisian qualifier Ons Jabeur posted the first upset of the tournament, beating 14th-seeded Anastasia Pavlyuchenkova of Russia 7-6 (6), 2-6, 6-4.
Samantha Stosur of Australia defeated Chinese qualifier Zhang Kai-Lin 6-3, 6-3, Caroline Garcia of France beat Johanna Larsson of Sweden 6-3, 6-3 after saving all four break points she faced in the encounter.
Mona Barthels of Germany made good on her wildcard offering by outplaying former top-ranked Jelena Jankovic of Serbia 6-1, 6-3.
Barthel's reward for reaching the second round is an encounter with fellow German Angelique Kerber, who can regain the No. 1 ranking if she wins the Dubai title.