Serbian qualifier Vesna Dolonc battled from a set down to upset former winner Dominika Cibulkova to advance to the second round of the joint ATP and WTA Kremlin Cup here on Tuesday.
Dolonc, 24, came through 3-6, 7-5, 6-3 winner against ninth seed Slovak Cibulkova, who won her first WTA title here in 2011.
The opponents traded breaks twice before Cibulkova made a break in the eighth game to clinch a 1-0 lead in 43 minutes.
In the second, the rivals continued trading breaks but this time Dolonc, who is 92nd in the WTA rankings, acted with more accuracy to level at one set all after one hour 43 minutes on court.
In the deciding set Dolonc made the winning break in the sixth game to take the set and the match in two hours 17 minutes.
Spanish sixth seed Carla Suarez Navarro upset home hope Vera Dushevina to ease into the second round.
The 25-year-old won through 6-4, 6-3 in one hour 19 minutes in her first meeting with 121st-ranked lucky loser Dushevina.
"She (Dushevina) has already played three qualifying matches here so she was well adjusted to the surface. I needed to be 100-percent to win today," Suarez Navarro said.
Top-seeded Angelique Kerber, coming off her third career title in Linz, Austria, last weekend, withdrew from the tournament on Monday with an abdominal strain.
In the ATP section of the event Italy's unheralded Paolo Lorenzi battled back from a set down to book a place in the second round after compatriot Filippo Volandri retired with a hip injury.
Volandri, ranked 91st, produced three breaks in the first set for a 1-0 lead as his 31-year-old rival replied with two breaks.
No big serves were produced in the second before the seventh game when Volandri, 32, broke his opponent's serve again to gain a 5-3 advantage.
But Lorenzi refused to surrender and survived a match point before breaking back twice to level at one set all after one hour 39 minutes on court.
In the deciding set Lorenzi, ranked 83rd, broke again for a comfortable 4-1 lead before Volandri withdrew injured.
Lorenzi next meets another compatriot and defending champion Andreas Seppi, who was seeded second here and enjoyed an opening round bye.
"It was a very tough and close match. He (Volandri) had a match point so I was lucky I managed to survive," Lorenzi said.
"It wasn't easy to play against him because we are very good friends. This morning we warmed up together. It's not easy when you know each other so well."