- Second seed Petra Kvitova loses to Li Na in Sydney International semifinals
- Kvitova would have become world No. 1 by winning the tournament
- 2011 French Open winner Li will play third seed Victoria Azarenka in Friday's final
- Top men's seed Juan Martin del Potro beaten by Marcos Baghdatis in quarterfinals
Petra Kvitova's hopes of beginning next week's Australian Open at the top of the women's tennis rankings ended on Thursday when the world No. 2 failed to reach the final of the Sydney Invitational.
The rising Czech star knew victory over Li Na in the semis would give her a chance to usurp Caroline Wozniacki by winning Friday's title match, but the 21-year-old lost 1-6 7-5 6-2 to China's defending champion.
The 2011 Wimbledon winner squandered a great chance to go through as she led 3-1 in the second set against Li, who also earned her first grand slam last year at the French Open.
But the fourth seed battled back, winning five straight games to level the match and then 12 of the last 13 points in the third to wrap up victory.
"In the beginning I played really fast and well," Kvitova told the WTA Tour website. "It's normal if you play too well, you will come down a little bit.
"That was the problem. It's life. She played very well. Many of us can be at the top, and she's one of us."
Li was pleased with her form, after reaching her first WTA final since becoming China's first grand slam champion at Roland Garros last June.
"Yeah, I'm back," the 29-year-old said. "I'm feeling stronger, in the body and mind. I'm just trying to do better -- not like what I was doing the last half of last year."
Li's opponent in Friday's final will be third seed Victoria Azarenka of Belarus, who came from behind to earn a 1-6 6-3 6-2 win over Wozniacki's quarterfinal conqueror, Polish seventh seed Agnieszka Radwanska.
Wozniacki struggled with a wrist injury, but the 21-year-old Dane told reporters she hoped to take her place in the Melbourne line-up.
In the Sydney men's event, 2010 champion Marcos Baghdatis earned a shock 7-6 (9-7) 6-4 quarterfinal victory over top seed and former world No. 4 Juan Martin del Potro of Argentina.
Del Potro, the 2009 U.S. Open champion, wasted two set points in the tie-break before slipping to defeat in one hour and 40 minutes against the Cypriot, who reached the final of the 2006 Australian Open.
Baghdatis' reward was a semifinal against France's Julien Benneteau, who won 6-2 6-4 against U.S-based Russian Alex Bogomolov Jr.
Qualifier Denis Istomin continued his unlikely run in Sydney with a 6-4 7-6 (7-4) triumph over French third seed Richard Gasquet.
The Uzbekistani, who has not dropped a set in six matches at the tournament, will next face experienced Finn Jarkko Nieminen -- a 6-3 6-3 victor against American Bobby Reynolds.
In Tasmania, defending champion and home favorite Jarmila Gajdosova crashed out of the Hobart International women's event with a 2-6 6-3 6-2 loss to German qualifier Mona Barthel.
Barthel will face compatriot Angelique Kerber in the semifinals following the fourth seed's 6-0 3-6 7-5 win over Romania's Sorana Cirstea.
Belgian top seed Yanina Wickmayer will meet Israel's Shahar Peer in the other semi after easing past Romania's Simona Halep 6-4 6-0.
Sixth seed Peer went through when her Russian opponent Anna Chakvetadze was forced to retire due to severe leg cramps while trailing 4-6 6-4 1-0.
Australian teenager Bernard Tomic earned a place in the final of the Kooyong Classic exhibition event in Melbourne, beating France's world No. 15 Gael Monfils 6-4 4-6 7-6 (7/2).
The 19-year-old, ranked 37th, will next face either American world No. 8 Mardy Fish or Austria's Jurgen Melzer.