KEY BISCAYNE, Fla. -- Serena Williams overcame a big deficit Monday 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 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, but screamed encouragement during her comeback. She won despite 52 unforced errors, including 27 on her backhand.
In the half-empty stands, Williams fell behind in the sleepy atmosphere and one spectator shouted "Bor-ing!" early in the second set.
The 5-foot-3 Cibulkova kept Williams moving with shots into the corners and pounced on short shots to put away winners.
During changeovers, disco, salsa and Coldplay blared from the public address system. Williams eventually got going, her shots landing consistently just inside the lines. She won 10 consecutive points to begin her rally.
After sweeping the final five games of the second set, she went ahead to stay by breaking serve at love for a 2-1 lead in the final set. After closing out the victory with a 116-mph ace, she swung her fist in satisfaction.
Williams lost serve five times, hit 14 aces and had a 42-12 advantage in winners.