WIMBLEDON, England(AP) Defending champion Serena Williams put on a serving clinic Saturday, hitting 20 aces in a straight-sets win over Dominika Cibulkova that sets up a possible fourth-round matchup with former champion Maria Sharapova.
The top-seeded American had at least two aces in each of her eight service games and overpowered the 46th-ranked Slovak 6-0, 7-5 in the day's first match on Centre Court.
Williams won 37 of 43 service points and held at love five times. She won 19 of her first 20 service points, with Cibulkova putting only four returns in play in that stretch.
The first set lasted just 18 minutes, with Williams winning 25 of 31 points, serving six aces and hitting 12 winners. She finished the match with 37 winners.
Cibulkova, a semifinalist at the French Open last year, finally got on the scoreboard when she held serve for 1-1 in the second set. From then on, she kept the match competitive by holding serve, although she couldn't cope with Williams' serves.
Cibulkova saved a match point while serving at 4-5 with a crosscourt backhand winner, but Williams broke in the 12th game to close out the match.
Cibulkova - generously listed at 5-foot-3 - looked tiny next to the imposing 5-foot-9 Williams.
Williams, chasing her fourth Wimbledon title and 13th Grand Slam crown, will next face the winner of the match between Sharapova and Barbora Zahlavova Strycova. Sharapova beat Williams in the 2004 final, and is coming back into top form after right shoulder surgery in 2008.
Also Saturday, seventh-seeded Agnieszka Radwanska advanced with a 6-3, 6-1 win over Sara Errani of Italy. In a mild upset, 14th-seeded Victoria Azarenka - a quarterfinalist here last year - squandered a chance to serve out the first set and was ousted 7-5, 6-0 by Petra Kvitova of the Czech Republic.
A marquee women's fourth-round match on Monday will feature Belgians Justine Henin and Kim Clijsters, who are 12-all in career meetings.
A year ago, the two Grand Slam champions were retired, but career comebacks brought them back to Wimbledon - a tournament neither has won. Clijsters last played at the All England Club in 2006, Henin in 2007.
It's a great opportunity for both of us,'' Henin said.To play each other again in a Grand Slam, I think it's something we couldn't expect a year ago. It's going to be interesting, very exciting.''
Clijsters, now a mother, rejoined the tour after Wimbledon last year and made an improbable run to the U.S. Open title. Henin came back in January and was the runner-up at the Australian Open.
While Clijsters and Henin meet for the 25th time Monday, former juniors doubles partners Roger Federer and Jurgen Melzer will play each other for the first time.