Radwanska, the defending champion, cruised through the first set without facing a break point, but struggled in the final two sets, dropping serve five times to the 103rd-ranked wild card entry.
The Pole relied on her strong defense to close out the match in just under 2 1/2 hours, chasing down a well-placed drop shot and hitting a forehand crosscourt winner to set up match point.
In other matches, second-seeded Simona Halep, the 2015 champion, defeated Jelena Jankovic 6-1, 3-6, 6-3; third-seeded Johanna Konta routed Cagla Buyukakcay 6-2, 6-0; and Serbian qualifier Nina Stojanovic took out fifth-seeded Timea Babos 1-6, 7-5, 6-2.
Original author: AP