Top-ranked Victoria Azarenka saved two match points on Wednesday before rallying past Angelique Kleber of Germany 6-7 (11 ), 7-6 (2 ), 6-4 in her first match at the WTA Championships.

In the first match Wednesday Serena Williams proved that even when her serve is malfunctioning, she can still abeat a top player. Williams beat 2011 French Open champion Li Na of China 7-6 (1 ), 6-3 for her second win in round-robin matches to close in on the semifinals at the tournament for the top eight players in the world.

Both Azarenka and Kleber smashed rackets in the second, highly entertaining match.

Kleber, making her debut in the event, was down a break in the second set, but led 5-4 after prevailing in a game that went to nine deuces and lasted 13 1/2 minutes.

Azarenka then saved two match points before capturing the second tiebreaker. The Belarusian closed it out on Kerber's serve, hitting a forehand winner on her first match point.

Azarenka needs one more round-robin win to secure the No. 1 ranking for the year.

In the earlier match Williams had six double-faults and won only 51 percent of points on her first serve. But Li also struggled on serve - there were eight breaks in the first set and three more in the second.

At one point, Williams got so frustrated at dropping serve that she uncharacteristically smashed her racket.

Earlier, defending champion Petra Kvitova withdrew from the tournament because of a viral illness and was replaced by Samantha Stosur.