It's a good thing the China Open had such a stellar field.

Even as big names continue to drop out, the schedule still boasts many of the world's best players, including French Open champion Li Na.

Enjoying a Grand Slam caliber status, the annual tournament attracted all the available top 48 women players and most of the top 35 males to fight for a total $6.1 million prize money at the Beijing Olympic Tennis Center from Oct 1-9.

Although the powerful Williams sisters - Serena and Venus - and Russian sensation Maria Sharapova have already announced they are pulling out, China's Li, Danish world No 1 Caroline Wozniacki and US Open winner Samantha Stosur will battle for the event's 1,000 ranking points.

Li, the current world No 7, is keen to gain redemption at this year's last WTA mandatory tournament after suffering early exits at both Wimbledon and the US Open.

A stomach spasm hampered Li's pre-match training on Wednesday morning, while her break-up with Danish coach Michael Mortensen triggered concern as well.

Drawn in the second half with Australia's Stosur, Li isn't scheduled to face a steep challenge until a potential fight against Italian veteran Roberta Vinci in the quarterfinals.

Stosur, who upset Li in their last meeting at the Cincinnati Open, has to overcome former top ace Jelena Jankovic in the third round to encounter Li.

Li vows to improve on her personal best performance last year, which saw her reach the semifinals.

But too many commercial activities seem to have affected her form.

Li signed her ninth sponsorship contract before the China Open, increasing her total endorsement income to almost $50 million, according to web portal Sohu.com.

China's other ace, Peng Shuai, will face Italian Flavia Pennetta - who won all the pair's previous five head-to-head matches - in the opening round before a possible quarterfinal matchup with No 7 seed Francesca Schiavone of Italy. Defending champion Wozniacki's first looming threat is a potential meeting with Wimbledon semifinalist Sabine Lisicki in the quarterfinals.

The second quarter of the draw will see a fierce battle featuring

Wimbledon champion Petra Kvitova, third-seeded ace Vera Zvonareva, Chinese veteran Zheng Jie and former No 1 Ana Ivanovic.

On the men's side, the reigning world No 1 and winner of three Grand Slams this year, Novak Djokovic, also withdrew due to a back injury suffered during a Davis Cup semifinal against Argentina last month.

American power hitter Andy Roddick will join Aussie wild-card holder Lleyton Hewitt and Spanish former world No 1 Juan Carlos Ferrero to fill the power void left by Djokovic and big-serving Swede Robin Soderling, who also quit with an injury.