The No. 10-seeded Cibulkova won despite losing her serve 10 times, double-faulting eight times and committing 51 unforced errors. There were 11 breaks in the first 12 games of the match.
Cibulkova collapsed to her back in jubilation when Radwanska's final shot sailed out. The runner-up at the Australian Open in January, Cibulkova advanced to the Key Biscayne semifinals for the first time.
Former top-ranked player Martina Hingis teamed with Sabine Lisicki and overcame three match points against Anabel Medina Garrigues and Yaroslava Shvedova to win 3-6, 7-6 (7), 10-7 and reach the semifinals in women's doubles.