PHOTOS: Radwanska soars in Sydney, Ferrer struts in NZ

Agnieszka Radwanska needed eight match points to finish off Li Na on Thursday but confirmed her fine pre-Australian Open form by maintaining her perfect start to the year and reaching the final of the Sydney International.

The Polish top seed was well worth the 6-3, 6-4 win over her Chinese opponent and will face Dominika Cibulkova in Friday's final after the Slovakian stunned German second seed Angelique Kerber 6-2 4-6 6-3.

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"I think I was really playing good tennis the last couple of days," said Radwanska, who also won the Auckland Classic last week and has started the year with eight straight wins. "I hope I can continue playing at this level."

Although Radwanska has had a busy schedule, Li was clearly tired after playing nine times in 10 days as well as managing to fit in a flight from China to Australia after winning last week's Shenzhen Open.

The Pole broke on Li's first service game and rarely looked back before stuttering to close out the match as she had in beating Yanina Wickmayer in Auckland last week.

"It was kind of like a deja vu from Auckland final," she said. "I'm really ready for the Australian Open. I will do of course everything to win that match tomorrow as well, and we'll see. I hope to win 16 matches in a row."

David Ferrer has played six fewer matches than Radwanska this year but really hit his stride on Thursday when he swept aside Lukas Lacko 6-2, 6-1 in his bid to win a fourth title at the Auckland Open.

The Spaniard, who like Radwanska will be seeded fourth at Melbourne Park next week, needed just 54 minutes to beat his Slovak opponent and set up a semi-final against Germany's Tommy Haas or French wildcard Gael Monfils.

The fifth seed in the men's draw for the year's first Grand Slam, Tomas Berdych, had a less enjoyable day at Kooyong where he was humbled 6-3, 6-2 by Australia's resurgent former world number one Lleyton Hewitt.

Hewitt, now 31 and ranked 82nd in the world, beat world number 15 Milos Raonic in his first round robin match on Wednesday and his 88-minute victory over Czech Berdych puts him into the final of the exhibition event.

There he will meet either Argentina's world number seven Juan Martin Del Potro or Cypriot Marcos Baghdatis, who face off at the Kooyong Classic on Friday.

"I'm just thrilled to be able to perform like this against quality players and on back-to-back days," Hewitt told reporters.

"I've had five tough sets in two days and that will hold me in good stead for next week."

Cibulkova added world number five Kerber to her list of top 10 victims in Sydney this week having already beaten Petra Kvitova and Sara Errani.

The men's event at the Sydney International warm-up reached the quarter-final stage with just one seed still standing after upsets and injury withdrawals ravaged the draw.

Frenchman Julien Benneteau, well rested after his second round tie on Wednesday went just four points before Radek Stepanek retired hurt, cruised past American qualifier Ryan Harrison 6-4, 6-2.

South Africa's Kevin Anderson joined him in the semi-finals with an equally straightforward 6-4 6-3 win over Denis Istomin of Uzbekistan.

Australian young gun Bernard Tomic faces defending champion Jarkko Nieminen in the quarter-finals later on Thursday with the winner going on to play third seed Andreas Seppi or Marcel Granollers in the last four.

Men's top seed John Isner, who lost to Harrison on Wednesday, pulled out of the Australian Open on Thursday because of a knee injury, leaving Sam Querrey as the only American men's seed at Melbourne Park this year.

Querrey overcame Canada's Jesse Levine 6-4, 7-6 in Auckland and will face Philipp Kohlschreiber in the semi-finals after the German beat Xavier Malisse 7-6, 6-4.