Maria Sharapova, Kim Clijsters out

WIMBLEDON, England -- Top-seeded Maria Sharapova was knocked out of Wimbledon on Monday, losing 6-4, 6-3 to Sabine Lisicki in the fourth round a month after completing a career Grand Slam.

Lisicki, a 15th-ranked German, simply outplayed the 2004 Wimbledon champion in windy, rainy conditions on Court 1 for her first career victory over Sharapova in four matches. She avenged a loss in the semifinals to Sharapova here last year.

Sharapova has been ranked No. 1 for 21 weeks, including this week, but has never won a tournament while ranked No. 1. It's the fifth time in the past six years that the No. 1 seed failed to reach the final on the women's side at the All England Club.Also advancing were four-time winner Serena Williams, second-ranked Victoria Azarenka and defending champ Petra Kvitova. Four-time Grand Slam champion Kim Clijsters lost in what she says was her final Wimbledon before retirement later this year.

Sharapova, who won the French Open four weeks ago for her fourth Grand Slam title, is the biggest name knocked out of the tournament since two-time men's champion Rafael Nadal was upset last week by Lukas Rosol.

After smacking a second-serve ace at 108 mph down the middle on her third match point, Lisicki collapsed to her knees on the grass and shook both fists. Among those cheering for Lisicki in the guest box was German NBA star Dirk Nowitzki of the Dallas Mavericks.

"It's just unbelievable," Lisicki said. "For the third time I've beaten the French Open champion here. I'm just so happy. I've lost the three previous meetings against her. Now I just played well and beat her for the first time."

Sharapova, who is 16-2 in Grand Slam matches this year, was trying to become the first woman since Williams in 2002 to win the French Open and Wimbledon in the same year.

"I just went for my shots. Really from the first point on I felt great out there," Lisicki said. "It's my favorite tournament. I love playing on grass; I love the crowd here. I just love it."

Lisicki reached the quarterfinals at Wimbledon for the third straight year and will next face another German, No. 8 Angelique Kerber, who drubbed Clijsters 6-1, 6-1. The 47th-ranked Belgian has said she will retire after the U.S. Open -- this time for good, having returned to the sport in 2009 after a two-year break. Clijsters, who has been dogged by injuries this year, walked off Court 3 with a brief wave.Azarenka cruised into the quarterfinals by routing former top-ranked Ana Ivanovic 6-1, 6-0.

Azarenka converted five of her seven break points and saved all three she faced in wrapping up the victory in little more than an hour.

The match was suspended by rain at 4-1 in the first set, forcing organizers to close the retractable roof over Centre Court. Azarenka continued to dominate when play resumed, and she finished with 19 winners compared to six unforced errors.

Azarenka, Williams and Kvitova are the only women's players left who have reached a Grand Slam final -- and they're all in the bottom half of the draw. Sharapova's defeat means there will be a first-time finalist from the top half.

Third-seeded Agnieszka Radwanska also advanced, beating Italian qualifier Camila Giorgi 6-2, 6-3.

The sixth-seeded Williams won the last three games to beat 65th-ranked wild card Yaroslava Shvedova of Kazakhstan 6-1, 2-6, 7-5 in cool and gusty conditions on Court 2. She improved to 10-1 lifetime in round of 16 matches at Wimbledon.

Williams hopped in joy after hitting a big forehand that forced an error by Shvedova on the first match point, ending a hard-hitting contest that lasted nearly two hours.

Shvedova, who became the first woman in the Open era to win a set without losing a point in her third-round match against Sara Errani, had never reached the fourth round at Wimbledon before this year.

"I didn't want to lose today and I thought, 'Just stay relaxed,'" Williams said. "I knew the whole match I could play better."

Williams will next face Kvitova, who rallied from a set and a break down to beat 2010 French Open champion Francesca Schiavone 4-6, 7-5, 6-1 in an error-filled match on Court 3.It was the second straight tough three-sets victory for Williams, who won 9-7 in the third to beat Jie Zheng in the previous round.

"I feel fine," she said. "I'm not tired. I'm not anything. I feel good. I feel like, bottom line, I can play so much better than what I have been playing. ... You know me. I'm never satisfied."

The match ended amid a slight drizzle, with play suspended on some of the other courts. Shvedova removed her glasses in the final two games to keep the lenses from getting wet.

"I think we both wanted to keep playing because it was so deep into the match," Williams said. "I didn't want to stop."

Williams finished with 35 winners, including 12 aces, and 13 errors. Shvedova had 24 winners and 20 errors.

The first player to reach the quarters was 37th-ranked Austrian Tamira Paszek, who beat Italy's Roberta Vinci 6-2, 6-2 to reach the final eight for the second year in a row.

Information from The Associated Press contributed to this report.