Radwanska survives, Li rolls in Miami

Fourth-seeded Agnieszka Radwanska survived a scare in her third-round match on Saturday, while Li Na of China cruised into the fourth round of the Sony Open.

The reigning Miami champion Radwanska was pushed to the limit against Slovak Magdalena Rybarikova, but the world No. 4 Pole hung on for a 7-6 (7-5), 2-6, 6-3 victory.

Radwanska will take on 16th-seeded Sloane Stephens in the quarterfinals after the upstart American advanced when former world No. 1 and seven-time major champion Venus Williams withdrew due to a lower back injury shortly before their third-round matchup.

The fifth-seeded Li, meanwhile, needed 78 minutes in a 6-2, 6-4 victory over American Varvara Lepchenko. She broke serve four times and had her serve broken just once.

Li, who won the season-opener in Shenzhen before finishing as the runner-up to Victoria Azarenka at the Australian Open, will next face Garbine Maguruza after the Spanish wild card upended ninth-seeded Caroline Wozniacki of Denmark, 6-2, 6-4.

Seventh-seeded Czech Petra Kvitova also slipped up on Saturday, as 30th-seeded German Kirsten Flipkens knocked off the former Wimbledon champ, 6-0, 4-6, 6-1.

Flipkens will next face Croatian wild card Ajla Tomljanovic, who fought off fellow wild card Andrea Petkovic of Germany, 0-6, 6-4, 7-6 (7-1).

Two other third-round battles are on Saturday's schedule, as top-seeded Serena Williams will meet Japan's Ayumi Morita in the opener of the night session, while Slovakian 13th seed Dominika Cibulkova will tangle with Switzerland's Romina Oprandi.