Klara Zakopalova ousted eighth seed and Czech compatriot Lucie Safarova out of the Kremlin Cup in the second round on Wednesday.
The 31st-ranked Zakopalova converted six of 13 break points to win 6-4, 6-4 and knock out last year's semifinalist Safarova, who is ranked 13 places above her at No. 18.
Zakopalova, who was stopped by eventual champion Dominika Cibulkova in the second round last year, plays Sam Stosur or Alize Cornet of France in the third round.
In the first round, Russia's Valeria Solovieva won a battle of two qualifiers against Ukraine's Elina Svitlona, prevailing 6-4, 6-2 to set up a second-round match with fourth seed Ana Ivanovic.
Ivanovic had a first-round bye.
In the men's draw, Japanese eighth seed Ito Tatsuma dispatched big-serving qualifier Konstantin Kravchuk of Russia 7-6(7), 2-6, 6-3, and will play Dutchman Igor Sijsling or second seed Andreas Seppi in round three.