Saint Petersburg - Germany's Annika Beck produced the first upset of the WTA St Petersburg Ladies Trophy on Monday ousting seventh seeded Dutchwoman Kiki Bertens 7-5, 3-6, 6-4.
It was Beck's first win over Bertens in their seventh meeting with the upset coming after the Dutch player had looked to be cruising early at the Sibur Arena.
The 25-year-old Bertens raced to a 5-3 lead and was serving for the opening set only for her 22-year-old rival to move a gear, reeling off four games for a one-set advantage after 50 minutes.
Bertens rallied in the second but floundered in the third, hitting 67 unforced errors throughout the match, with Beck coming through in two hours 19 minutes.
"It was a great match and my season's first win," said a delighted 67th-ranked Beck.
"I had low expectations as there are so many great players here.
"It's especially good that I have a day off tomorrow. I will definitely watch the match of my next opponent and will prepare good for that."
The German next plays either Kazakh Yulia Putintseva or Sweden's Johanna Larsson for a place in the quarter-finals.
Earlier Australia's Daria Gavrilova beat Russian wildcard Anna Kalinskaya 6-4, 7-5, after another Russian wildcard Natalia Vikhlyantseva cruised past Yaroslava Shvedova of Kazakhstan 6-3, 6-4.
Moscow-born Gavrilova will next play third-seeded Russian Svetlana Kuznetsova in a replay of the last year's Kremlin Cup final.
"I'm pleased with the result but not with my performance today," Gavrilova said.
"Maybe it was acclimatisation after Australia but I need to boost my performance in every aspect to beat Svetlana."