Hewitt eventually won in five sets and the crowd had thinned by the time Williams and Shvedova took the court.
Williams recorded a 6-3, 6-1 victory to move her into the round of 16 against fellow American Sloan Stephens, who earlier defeated Jamie Hampton 6-1, 6-3.
Radwanska, seeded third, needed nearly 2 hours to get by 32nd-seeded Anastasia Pavlyuchenkova 6-4, 7-6 (7-1). She dropped her serve once in each set but had a pair of breaks of her own to win the first set and survived the tiebreaker in the second to advance.
Li, the No. 5 seed, knocked out 30th-seeded Laura Robson, winning more than two-thirds of the points on serve and allowing Robson just two break opportunities. Li went 9-for-9 on points when she approached the net.
In other third-round matches Friday, Carla Suarez Navarro defeated Zheng Jie 6-3, 6-4, Angelique Kerber was a 6-0, 6-4 winner over Kaia Kanepi, Ekaterina Makarova took out Sabine Lisicki 6-4, 7-6 (7-5) and Jelena Jankovic defeated Kurumi Nara 6-4, 7-6 (7-5).
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