Dylan Martinez / Reuters

Sloane Stephens of the U.S. reacts during her singles match against Petra Cetkovska of the Czech Republic.

updated 1:38 p.m. ET June 27, 2012

WIMBLEDON, England - American teenager Sloane Stephens says maturity is making her more of a threat, and she's into the third round at Wimbledon.

Later, Caroline Wozniacki wasted two match points in the second set before losing 5-7, 7-6 (4), 6-4 to Tamira Paszek of Austria in the first round in a match that lasted more than 3 hours.

The former top-ranked Dane saved four set points in the first set but then failed to convert two break points when leading 5-4 in the second. Paszek then erased an early break in the decider but failed to serve out the match at 5-3, only to break the seventh-seeded Wozniacki again to clinch the victory.

The match was halted because of rain on Tuesday with the score at 2-2 in the first set and it was interrupted again by showers that forced organizers to slide the retractable roof out over Centre Court.

Stephens saved five set points in the opening set Wednesday and beat No. 23 Petra Cetkovska 7-6 (6), 4-6, 6-3.

"I'm 19 and I do still have some lapses," Stephens said. "They're less now than I used to have in the past. I really don't get as upset when I lose points now. I'm not that emotional anymore."

Wimbledon (June 22-July 8) Toby Melville / Reuters Magnificent 7th Roger Federer won his record-tying seventh Wimbledon title Sunday, beating Andy Murray 4-6, 7-5, 6-3, 6-4 under a closed roof on Centre Court. Full story Tennis.com: Federer shows his game remains timeless Oxfam won big when Federer won 7th Wimbledon title Serena powers way to 5th Wimbledon title Opinion: Plan for 'grunt-o-meter' is a scream Men's and women's scores from Wimbledon

"I don't know what was going on," Stephens said. "It was ridiculous, but then I served great the rest of the game."

Ranked 59th, Stephens is playing at Wimbledon for the first time. She's coming off her first run to the fourth round at a Grand Slam tournament, which came this month at the French Open.

"It takes time to build your concentration and focus," she said. "It has gotten better and better with time, and I think playing better players helps."

Stephens, the daughter of a former NFL star and a college All-American swimmer, said some of her confidence comes from feeling she belongs on the tour. She has forged friendships with many players, including 13-time Grand Slam champion Serena Williams.

During the Fed Cup tie against the Ukraine in April, Stephens and Williams hung out together at the Kharkiv resort where they were staying. They even enjoyed bonding adventures such as driving a golf cart around a course in the dark.

"That's my girl," Stephens said of Williams. "She's so goofy. We're just friends, we get along well. We click. About everything we talk about we agree.

"She's funny and we're always laughing. We can't be serious. People don't really see who she is because they only see what she is on court. But who cares? Her friends know who she is."

Stephens faces No. 15 Sabine Lisicki in the third round.

Heather Watson became the first British woman to reach the third round since 2002 when she defeated American Jamie Hampton 6-1, 6-4.

Sara Errani needed only seven seconds to complete a rain-interrupted win, and she didn't even have to hit a ball.

Errani led American CoCo Vandeweghe 6-1, 5-3 and held the advantage one point from victory when their match was halted Tuesday evening. They returned to Court 16 some 18 hours later, and when Vandeweghe double-faulted into the net on the first point, Errani had the win.

Reigning U.S. Open champion Samantha Stosur was upset by 72nd-ranked Arantxa Rus 6-2, 0-6, 6-4. Stosur, who was seeded fifth, fell to 6-10 at Wimbledon.

No. 13 Dominika Cibulkova lost to Klara Zakopalova 6-4, 6-1. Former No. 1 Ana Ivanovic beat Maria Jose Martinez Sanchez 6-3, 3-6, 6-3.

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Headlines

• Label

Murray retires from match against Granollers

Serena gains sisterly revenge on Robson in Rome

Brazilian player received 8 1/2-month doping ban

Janowicz upsets Tsonga at Italian Open

Djokovic and Federer show improved form in Rome

Serena subdues Sharapova to defend Madrid title

Djokovic recovers from Madrid shock to win in Rome

Wozniacki upset in Rome, clay struggles continue