Mason, OH (Sports Network) - Sizzling-hot Serena Williams and top seed Agnieszka Radwanska were a pair of third-round winners Thursday at the WTA's Western & Southern Open. Venus Williams also secured a berth in the quarterfinals at this $2.168 million event.

The second-seeded Serena took care of Radwanska's younger sister Urszula, a qualifier this week, 6-4, 6-3 in 70 minutes.

The former world No. 1 Serena is currently riding a torrid 19-match winning streak since being stunned in the first round at the French Open in June. The 14-time Grand Slam champ is seeking a fourth straight tournament title after posting big wins at Wimbledon, Stanford and the London Olympic Games.

Serena's quarterfinal opponent will be quality German left-hander Angelique Kerber.

Meanwhile, the Polish world No. 3 Agnieszka Radwanska, who was last month's Wimbledon runner-up to Serena, outlasted American wild card Sloane Stephens 6-1, 4-6, 6-4 on the hardcourts at the Lindner Family Tennis Center.

The wild card Venus smacked seven aces in blowing past seventh-seeded Italian Sara Errani 6-3, 6-0 in 61 minutes. Errani was a surprise French Open runner- up two months ago.

Venus' opponent on Friday will be reigning U.S. Open champion Sam Stosur.

Also on Day 4 in suburban Cincinnati, a third-seeded Stosur, of Australia, pasted Russian Ekaterina Makarova 6-1, 6-3, while fourth-seeded Czech Petra Kvitova whipped Chinese Peng Shuai 6-2, 6-2, and a fifth-seeded Kerber topped Czech qualifier Andrea Hlavackova 6-4, 7-6 (7-5). The 2011 Wimbledon champion Kvitova is fresh off her title in Montreal on Monday.

The Sports Network