DOHA, Qatar -- Top-seeded Li Na, playing her first match since winning the Australian Open last month, beat Magdalena Rybarikova of Slovakia 6-1, 5-7, 6-2 in the second round at the Qatar Open on Wednesday.
Third-seeded Petra Kvitova of the Czech Republic outlasted Venus Williams of the United States 6-2, 2-6, 7-6 (7) in a match lasting 2 hours, 32 minutes.
Li raced to a 5-0 lead in the opening set but couldn't keep her momentum going in the second when, at 5-5, Rybarikova won the next two games.
With a 3-2 lead in the decider, Li won the final three games of the match.
The 48th-ranked Williams wasted a match point in the third set tiebreaker.
"I put myself in a great position to win the match, which for me is the positive that I take out of this match," said Williams, who was leading the set 4-1 and had three break points on Kvitova's serve in the sixth game, but couldn't secure the 5-1 advantage.
Kvitova, playing her first match since being upset in the Australian Open first round, refused to give in.
"I felt more confident on the court and was really fighting hard for every ball," Kvitova said.
Serving for the match at 5-4, Kvitova squandered one match point at 40-30, and then double-faulted away the game.
Also, second-seeded and three-time tournament semifinalist Agnieszka Radwanska of Poland defeated Sorana Cirstea of Romania 7-5, 6-0.
Angelique Kerber (6), Caroline Wozniacki (8), Ana Ivanovic (9) and Samantha Stosur (12) all lost their second round matches on Wednesday.