Melbourne - A dominant Maria Sharapova routed another hapless opponent Wednesday as ninth seed Samantha Stosur flopped out of the Australian Open, amid increasing speculation about Serena Williams' fitness.
The world number two Russian handed a tennis lesson to young Japanese Misaki Doi in a one-sided 6-0, 6-0 rout to book a potential third clash with seven-time Grand Slam winner Venus Williams.
Sharapova also thrashed her first round challenger 6-0, 6-0 to become the first woman since Wendy Turnbull at the Australian Open in 1985 to bag two double bagel Grand Slam wins in a row.
"I just wanted to get out on court because I haven't had many matches this year," she said. "I was really eager to get on court again."
Her flawless performance in just 47 minutes was in stark contrast to Australia's Stosur, who threw away the last five games to hand China's Zheng Jie passage to the next round.
Stosur, who suffered first-round flops at WTA events in Brisbane and Sydney this year, was leading 5-2 in the third set but choked in front of her home fans and double faulted to hand Zheng victory 6-4, 1-6, 7-5.
While Stosur was on court, Serena Williams held a closed indoor training session, fuelling speculation about her fitness after she painfully rolled her ankle on court Tuesday.
The defiant 15-time Grand Slam champion, a hot tournament favourite, claimed only a "fatal" injury would prevent her contesting the second round against Spain's Garbine Muguruza on Thursday.
But she chose to move her scheduled session from court 17 to the indoor training facility and closed it to the media and public, disappointing hundreds of spectators who wanted to watch.
Elsewhere, fourth seed Agnieszka Radwanska built on her sizzling start to the season to progress along with Chinese star Li Na and fifth seed Angelique Kerber.
Radwanska stormed to her 11th straight victory of the year as she carried the form shown in winning titles at Auckland and Sydney in the lead-up to the year's opening Grand Slam.
The Pole beat Irina-Camelia Begu 6-3, 6-3 as she aims to improve on her three quarter-final appearances in Melbourne and now faces Britain's Heather Watson.
While Radwanska had no dramas in overcoming the Romanian, former French Open champion Li was erratic in her 6-2, 7-5 victory over Olga Govortsova of Belarus.
Li sailed through the first set but struggled in the second, before finally knuckling down to claw back four games in a row to progress.
"She started the second set much better so I'm just happy to win," said Li, adding that she was confident of adding to her solitary Grand Slam title in 2011. "Australia for me -- I really believe I can win this Grand Slam."
The hardcourts seem to suit Li's style of play and she made the final at Melbourne Park in 2011, losing to Kim Clijsters, and was a semi-finalist in 2010.
In contrast to Li's struggle, Germany's Kerber, who broke through last year with WTA titles in Paris and Copenhagen which pushed her to her current rank of five, looked comfortable in her 6-3, 6-1 win over Czech Lucie Hradecka.
"Of course I have a lot of confidence from last year," said Kerber. "I beat a lot of good players and reached the top 10, top 5. I'm just enjoying being where I am right now, and just having fun also on the court and off site."
Results from day three of the Australian Open on Wednesday:
Agnieszka Radwanska (POL x4) bt Irina-Camelia Begu (ROM) 6-3, 6-3
Angelique Kerber (GER x5) bt Lucie Hradecka (CZE) 6-3, 6-1
Kirsten Flipkens (BEL) bt Klara Zakopalova (CZE x23) 6-1, 6-0
Julia Goerges (GER x18) bt Romina Oprandi (SUI) 6-3, 6-2
Valeria Savinykh (RUS) bt Dominika Cibulkova (SVK x15) 7-6 (8/6), 6-4
Li Na (CHN x6) bt Olga Govortsova (BLR) 6-2, 7-5
Ekaterina Makarova (RUS x19) bt Stephanie Foretz Gacon (FRA) 6-3, 6-3
Madison Keys (USA) bt Tamira Paszek (AUT x30) 6-2, 6-1
Zheng Jie (CHN) bt Samantha Stosur (AUS x9) 6-4, 1-6, 7-5
Sorana Cirstea (ROM x27) bt Kristyna Pliskova (CZE) 1-6, 6-3, 6-2
Maria Sharapova (RUS x2) bt Misaki Doi (JPN) 6-0, 6-0
Nicolas Almagro (ESP x10) bt Daniel Gimeno-Traver (ESP) 6-4, 6-1, 6-2
Kei Nishikori (JPN x16) bt Carlos Berlocq (ARG) 7-6 (7/4), 6-4, 6-1
Sam Querrey (USA x20) bt Brian Baker (USA) 6-7 (2/7), 1-1 ret
Jurgen Melzer (AUT x26) bt Roberto Bautista Agut (ESP) 6-7 (4/7), 6-3, 6-7 (3/7), 6-3, 6-2
Stanislas Wawrinka (SUI x15) bt Tobias Kamke (GER) 6-3, 7-6 (7/4) ret
Jerzy Janowicz (POL x24) bt Somdev Devvarman (IND) 6-7 (10/12), 3-6, 6-1, 6-0, 7-5
Tomas Berdych (CZE x5) bt Guillaume Rufin (FRA) 6-2, 6-2, 6-4
David Ferrer (ESP x4) bt Tim Smyczek (USA) 6-0, 7-5, 4-6, 6-3
Marcos Baghdatis (CYP x28) bt Tatsuma Ito (JPN) 3-6, 6-3, 6-2, 6-2
Evgeny Donskoy (RUS) bt Mikhail Youzhny (RUS x23) 3-6, 7-6 (7/4), 6-2, 3-6, 6-3