Steely Li Na confident of halting Maria Sharapova

Record-breaking Maria Sharapova will hope to capitalise on Serena Williams' demise to snatch her fifth Grand Slam title -- but first she'll have to get past a determined Li Na in the semis.

The tall Russian was quickly installed as bookmakers' favourite after a limping Williams was upset by teenager Sloane Stephens, who will face 2012 champion Victoria Azarenka in the last four on Thursday.

Sharapova has been in terrifying form at the year's opening Grand Slam, running through five matches for the loss of just nine games, a new tournament record.

But Li is relaxed, fitter and perhaps steelier under new coach Carlos Rodriguez, and she can also draw on her 2011 performances, when she defeated the Russian at the French Open the way to becoming Asia's first Grand Slam champion.

"She's a more aggressive player on the court. Also she's tough. She's fighting a lot," said Li, when asked how Sharapova's game had improved.

"Should be a tough match. So we'll see Thursday."

Li has shown she is comfortable at Melbourne Park, after reaching the 2011 final where she was beaten by Kim Clijsters, as well as making two other semi-finals.

And the Chinese world number six showed she is back on top of her game in the quarter-finals, when she halted the 13-match winning streak of Poland's Agnieszka Radwanska.

Li has already picked up one title this year, in Shenzhen, and the 30-year-old seems to have banished the dreadful run of Grand Slam form which followed her 2011 win in Paris.

"She certainly stepped up her game. I think at different times in a player's career you need that extra motivation, you might need a change," said Sharapova.

"She's been there, she's done that -- she's a Grand Slam champion. It wasn't like she needed someone to come in and fix her game. I don't think that was really the plan.

"But sometimes when you just have a different surrounding and a new voice, they might be saying the same things but it just gets to you a little bit differently and your motivation changes."

The two also have oddly intertwined off-court affairs as they share an agent, Max Eisenbud, and Sharapova is coached by Thomas Hogstedt, who previously worked with Li.

"We've played against each other so many times before Thomas was my coach and Max has been my manager since I was 11 years old. We know each other's game. It has nothing to do (with anything)," Sharapova insisted.

However, the Russian was not amused when asked whether Li could help her by taking a bag of her new line of sweets, Sugarpova, to China.

"I think I can do that, too," Sharapova snapped.

Meanwhile America's Stephens, 19, will be basking in the glow of her defeat of injury-hit 15-time Grand Slam winner Williams, in the biggest shock of the tournament, when she walks out against Azarenka.

"I was stretching, and I was like, 'I'm in the semis of a Grand Slam'. I was like, 'Whoa'. It wasn't as hard as I thought. But it's pretty cool," she said, immediately after her 3-6, 7-5, 6-4 win.

The confident teenager was vague on her game plan but against Williams, she showed she has the shots and the temperament to cause problems for the world number one.

"It's going to be a totally different match. I'm just going to go out and play my best," she said. "Do what I do really well and just play my game. Just hopefully play well again."