Dhaka, April 5 -- Russia's Anna Kalinskaya came through at the crucial moments while beating second-seeded Madison Keys of the United States 6-2, 6-4 on Thursday in the third round of the Credit One Charleston (S.C.) Open.

Kalinskaya took advantage of four of her five break-point opportunities, and she saved seven of Keys' eight break points.

In the quarterfinals, Kalinskaya will oppose another U.S. player, Sofia Kenin, who topped fifth-seeded Daria Kasatkina of Australia 6-3, 7-6 (7).

Top-seeded Jessica Pegula eased into the quarterfinals with a 6-3, 6-2 win over Australia's Ajla Tomljanovic. Fourth-seeded Emma Navarro won an all-U.S. matchup against 15th-seeded Ashlyn Krueger, 4-6, 6-4, 6-2.

Also moving into the quarterfinals were t...