Serena Williams has overcome a big deficit in her fourth-round match at the Sony Open to beat Dominika Cibulkova 2-6, 6-4, 6-2.
The top-ranked Williams, seeking her sixth Key Biscayne title and her first since 2008, was down a service break trailing 4-1 in the second set Monday before she won five straight games. She swept the final three games and served out the match at love with three aces.
Williams' opponent in the quarterfinals will be No. 5-seeded Li Na, who beat wild card Garbine Muguruza 7-6 (6), 6-2.
Williams was flat-footed and impassive for much of her match against the No. 13-seeded Cibulkova. She was screaming encouragement to herself during the comeback.
She won despite 52 unforced errors, including 27 on her backhand.