Serena, Radwanska reach Cincy QFs

Sizzling-hot Serena Williams and top seed Agnieszka Radwanska were a pair of third-round winners Thursday at the WTA's $2.168 million Western & Southern Open.

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

The former world No. 1 Williams 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 Olympic Games in London.

Williams' 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 Williams, outlasted American wild card Sloane Stephens 6-1, 4-6, 6-4 on the hardcourts at the Lindner Family Tennis Center.

Also on Day 4, third-seeded U.S. Open champ Sam 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.