MELBOURNE, Australia (AP) Maria Sharapova advanced to the third round of the Australian Open without losing a game, and No. 4 Agnieszka Radwanksa extended the best winning streak of the year to 11 matches on Wednesday.
Sam Stosur couldn't get the same traction, wilting again under the pressure of expectations at home. The 2011 U.S. Open champion twice failed to serve out the match before losing 6-4, 1-6, 7-5 to China's Zheng Jie in a second-round upset.
No. 2-ranked Sharapova, the runner-up here last year, had a 6-0, 6-0 win over Misaki Doi in 47 minutes, conceding just 15 points to the Japanese player. The reigning French Open champion hasn't seemed to be troubled at all by a right collarbone injury that ruled her out of a warm-up tournament in Brisbane earlier this month.
Sharapova beat fellow Russian Olga Puchkova 6-0, 6-0 in the first round, and has so far only spent 1 hour, 42 minutes on court in two matches at Melbourne Park.
``I've been playing really aggressively and doing the right things,'' Sharapova said. ``It's not easy to be up so much because you can have a few let-downs. You just have to try to concentrate.''
No. 9 Stosur couldn't close out her opponent. She was leading 5-2 in the third set and was only two points from advancing to the third round before Zheng, the first Chinese player to reach a Grand Slam semifinal when she made the last four at Wimbledon in 2008, reeled off five straight games to end Australia's involvement in the women's draw.
``Sorry everybody in the stands,'' Zheng said. ``It was a very good win for me I think.''
It extended a miserable run at home for Stosur, who lost in the first round here last year in her first major after beating Serena Williams in the U.S. Open final. Her opening win Monday was her first victory in five matches at home.
Radwanska had earlier rolled into the third round with a 6-3, 6-3 victory over Romania's Irina-Camelia Begu and remains unbeaten this year, including titles at warm-up tournaments this month at Auckland and Sydney.
``I can play even better,'' said Radwanska, who lost last year's Wimbledon final to Serena Williams. ``I didn't really expect I could win that many matches in a row, and hopefully I can keep going.''
Her last two trips to the Australian Open have ended in quarterfinal losses to the eventual champion - Kim Clijsters in 2011 and Victoria Azarenka last year.
With top-ranked Azarenka and Williams in the other half of the draw, Radwanska's main obstacles to reaching the final are 2011 French Open champion Li Na, who beat Olga Goortsova of Belarus 6-2, 7-5 to reach the third round, and potential semifinal rivals Sharapova or No. 5 Angelique Kerber of Germany.
Kerber advanced with a 6-3, 6-1 win over Lucie Hradecka.
Williams hurt her ankle in her opening victory Tuesday, causing speculation that her bid for a third consecutive major title Open could be in jeopardy. She has only lost one match since her first-round exit at the French Open last year. Williams canceled an outdoor practice session and moved it indoors, beyond the media glare, on Wednesday afternoon.
In women's second-round matches, No. 11 Marion Bartoli beat Serbian qualifier Vesna Dolonc 7-5, 6-0, No. 18 Julia Gorges beat Romina Oprandi 6-3, 6-2, Russian qualifier Valeria Savinykh upset No. 15 Dominika Cibulkova 7-6 (6), 6-4 and Kirsten Flipkens of Belgium ousted No. 23 Klara Zakopalova 6-1, 6-0 and 17-year-old American wild-card Madison Keys beat No. 30 Tamira Paszek of Austria 6-2, 6-1.
On the men's side, No. 4-ranked David Ferrer needed five match points before clinching a 6-0, 7-5, 4-6, 6-3 win over American Tim Smyczek, who got into the main draw as a lucky loser from qualifying.
Fifth-seeded Tomas Berdych beat Guillaume Rufin of France 6-2, 6-2, 6-4, and No. 10 Nicolas Almagro and No. 16-ranked Kei Nishikori also moved on. No. 24 Jerzy Janowicz of Poland rallied from two sets down to overpower India's Somdev Devvarman 6-7 (10), 3-6, 6-1, 6-0, 7-5.
No. 20 Sam Querrey advanced when fellow American Brian Baker retired in the second set with what appeared to be a right knee injury and next plays No. 15 Stanislas Wawrinka.
Baker, who returned to the tour last year after missing almost six seasons with a variety of injuries, won a first-set tiebreaker and was level at 1-1 on serve in the second. He was later pushed from Court 6 in a wheelchair.
``Yeah, he's the last person that deserves anything like that with his five or six surgeries already,'' Querrey said. ``He does everything right, treats his body great, just trying to come back, and then something like that happens, it's just so unlucky.''
Williams had a moment on Day 2 when she felt like her tournament could be over.
Flat on her back, her sore right ankle raised and her hands covering her face, she tried to block out thoughts that her bid for a third straight Grand Slam title might be ruined.
``I almost panicked, and I thought, `I can't do that,''' she said. ``I just have to really remain calm and think things through.''
Williams beat No. 110-ranked Edina Gallovits-Hall 6-0, 6-0 in 54 minutes, but the match may have taken a toll.
Williams expects to at least start her second-round match Thursday against Spain's Garbine Muguruza.
``Oh, I'll be out there,'' Williams said. ``I mean, unless something fatal happens to me, there's no way I'm not going to be competing. I'm alive. My heart's beating. I'll be fine.''