KEY BISCAYNE, Fla -

Five-time champion Serena Williams has advanced to the Sony Open semifinals and tied the women's record for career victories in the tournament by beating No. 5-seeded Li Na 6-3, 7-6 (5).

Williams overcame six double-faults Tuesday and rallied in the second set from a 5-2 deficit. She hit six winners in the tiebreaker, including a forehand passing shot cross-court on the final point.

Williams, who won her most recent Key Biscayne title in 2008, improved to 59-7 in the tournament. Steffi Graf, another five-time champion, went 59-6.

No. 3 David Ferrer advanced to the men's quarterfinals by beating No. 13 Kei Nishikori 6-4, 6-2. Ferrer's next opponent will be unseeded Jurgen Melzer, who rallied past Albert Ramos 2-6, 6-3, 6-3.