Maria Sharapova reaches 4th round

WIMBLEDON, England -- Maria Sharapova struggled with her serve again in windy conditions at Wimbledon and rallied from a break down in the second set Friday to beat Hsieh Su-Wei of Taiwan 6-1, 6-4 and reach the fourth round.

The top-ranked Russian dominated the first set, breaking Hsieh three times and looking headed for an easy victory. But as the wind picked up in the second set, Sharapova's serving problems surfaced again. She double-faulted five times in the second, including one serve that bounced on her own side of the net, and trailed 4-2 before taking the last four games.

"Considering the conditions, I'm pretty happy with the way I played," she said.

Sharapova is looking for her second Wimbledon title after losing last year's final to Petra Kvitova. She is coming off her first French Open title, which completed a career Grand Slam.

Kim Clijsters reached the fourth round of Wimbledon on Friday when 12th-seeded Vera Zvonareva retired with an apparent respiratory problem when trailing 6-3, 4-3.

Zvonareva was coughing loudly during the match and the 2010 finalist was in tears as she needed a medical timeout at 2-1 in the second set. The trainer took her pulse and she was examined with a stethoscope before resuming play, but had to retire four games later.

Clijsters said "I think she was having difficulties breathing" and that it's "sad to see her end the tournament this way."

The Belgian is playing in her last Wimbledon as she plans to retire after this year's U.S. Open. She will next play No. 8 Angelique Kerber, who beat Christina McHale of the United States 6-2, 6-3.

American teenager Sloane Stephens failed in her bid to reach the fourth round at a second straight Grand Slam tournament, losing in three sets to Sabine Lisicki of Germany.

The 15th-seeded Lisicki, a semifinalist here last year, found some consistency on her groundstrokes in the final set to complete a 7-6 (5), 1-6, 6-2 victory.

"I definitely wasn't overpowered by her," said Stephens, who was playing in front of her mother on Court 3. "I was 5-2 up in the first-set tiebreaker. I didn't win it and felt, 'Wow, this is kind of ridiculous.' Second set I played pretty well, played more aggressive but the third set got away from me."

The 19-year-old Stephens was playing in her first Wimbledon and looking to reproduce her exploits from the French Open, where she reached the fourth round in her best run at a major.

However, she lost five straight points after leading 5-2 in the first-set tiebreaker before recovering to win five consecutive games in a dominant second set.

Stephens' performances in the slams over the past month hint at a bright future.

Although she has missed out on her main aim of 2012 -- making the U.S. team for the Olympics -- the daughter of former NFL player John Stephens has risen from No. 85 at the start of the year to a current ranking of No. 59, one place behind Venus Williams. She will be ahead of Venus by the time the new rankings come out after Wimbledon.

"At the beginning of the summer, I wanted so badly to make the Olympics I just couldn't play tennis at all. I couldn't focus, couldn't do anything," she said. "Then, I kind of realized that I should just work hard, do what I have to do and I will be fine. I was this close to making the Olympics but I'm still pleased with the way I've played and am playing now."

Lisicki was impressed with what she saw from Stephens during Friday's match.

"She's a great, talented, young American girl," Lisicki said. "It's good to see someone coming up from the States after the Williams sisters. You know, we'll see what happens within the next couple of years."

Information from The Associated Press contributed to this report.