Former world No. 1 Victoria Azarenka was an easy third-round winner at the $2.37 million Western & Southern Open, a hardcourt U.S. Open tune-up.

The second-seeded Belarusian star, the reigning Australian Open champion and U.S. Open runner-up, handled Slovak and recent Washington, D.C., titlist Magdalena Rybarikova, 6-3, 6-4, at the Lindner Family Tennis Center.

Meanwhile, fourth-seeded former Wimbledon runner-up Agnieszka Radwanska pummeled Russian Elena Vesnina 6-0, 6-2, and in a rematch of last year's Cincinnati final, fifth-seeded and defending champ Li Na beat ninth-seeded German Angelique Kerber, once again, this time by a 6-4, 6-4 margin. Poland's Radwanska and China's Li will square off in the round of eight.

A Day-4 upset came when 12th-seeded Roberta Vinci toppled her good friend and doubles partner Sara Errani, this week's sixth seed, by a 6-4, 6-3 score. Vinci is now 2-1 versus her higher-ranked compatriot this year and 4-5 lifetime. Vinci upset Errani in a final in Palermo in their native Italy just last month.

Former top-ranked Serb Jelena Jankovic, seeded 14th, cut down 14th-seeded American Sloane Stephens, 3-6, 7-5, 7-5. The 2009 Cincy champ and 2011 runner- up Jankovic will face Vinci on Friday.

This week's champion will earn $426,000. The tournament is part of the U.S. Open Series, or the North American hardcourt events that lead up to the U.S. Open, which will commence August 26.