Li Na of China returns a ball during a match against South Africa's Chanelle Scheepers?in the second round of Sydney International on Jan. 10, 2012. [Source: Sina.com]

World No. 1 Caroline Wozniacki received some glowing words of support from French Open champion Li Na after both players flirted with early exits at the Sydney International yesterday.

Denmark's Wozniacki trailed Slovakia's Dominika Cibulkova 0-4 in the third set of their second round encounter before the top seed eked out a 7-5, 2-6, 6-4 victory. Chinese fourth seed Li was also taken the distance in a 2-6, 6-4, 6-1 win over South Africa's Chanelle Scheepers, digging deep to draw on her improved fitness garnered from an intensive off-season spent in Germany.

Despite holding the No. 1 spot for two years, Wozniacki's lack of a major title has left some observers to question her credibility but No. 5 Li believes the Dane deserves to be regarded as the best.

"I would like to say she's a really tough player," Li told reporters. "Really. I mean, every time I am against her, I'm tired and cramping. She has improved a lot on her forehand because I used to see her miss a lot on the forehand," she added.

"Now she doesn't have any mistakes. She has two years in a row as world number one and of course the goal for her now is to win a grand slam.

"It is not easy to do, but I think she will keep going and never give up."

Li said an extended match on another hot Sydney day was the perfect way to acclimatize for the Australian Open starting in Melbourne next week. "I have to get used to the heat," Li said.

"Melbourne will be the same weather, the same thing. At the beginning of the match I was feeling so relaxed. But she (Scheepers) can hit the ball so deep and every ball comes back. I was trying to hit too many winners."

Four weeks of fitness work in Munich during the off-season had paid off.

"Every day I had two hours for tennis and three hours for fitness. I did weights, jumping, footwork, everything... because I want my body to be healthy and fit for the whole year," she said.

Wimbledon champion Petra Kvitova, ranked No. 2, also struggled against an unseeded opponent before advancing to the quarterfinals with a 7-5, 3-6, 6-4 win over Alexandre Dulgheru of Romania. Also, third-seeded Victoria Azarenka of Belarus beat Jelena Jankovic of Serbia 6-4, 6-2 and seventh-seeded Agnieszka Radwanska of Poland defeated Andrea Petkovic of Germany 7-5, 6-4.