URUMQI -- Olympic and world table tennis champion Zhang Yining has been so mighty in the women's ping-pong that few would doubt she will win her fifth World Cup.

The world top-ranked Zhang, winner in 2001, 2001, 2004 and 2005, has been in a class of her own since the pencil-slim Beijinger clinched China's historic 100th Olympic gold medal in the Athens Games in 2004.

Her archrival and teammate Wang Nan, three-time winner, opted out of the September 29-October 1 tournament to give way to young players.

"Zhang has been virtually unbeatable since the 2004 Olympics," said Chinese women's team head coach Shi Zhihao. "She is the most consistent player in the team and none of the young players is able to match her in skills, tactics or mentality."

The annual World Cup, which features the world's top-ranked players and continental champions, is one of the most watched table tennis events in the world, rated third in importance, only after the Olympic tournament and the world championships.

If the impossible becomes a reality and Zhang suffers an early exit, Guo Yan, world runner-up to Zhang and currently ranked No. 3, will fill in for the title chase.

Chinese youngster Li Xiaoxia, ranked sixth, will have a title chance if her more fancied teammates fall in early rounds.

The Chinese women have never let go a single World Cup trophy since legendary Deng Yaping won the inaugural event in 1996. Wang Nan won in 1997, 1998, 2003 and Li Ju triumphed in the Cambodian capital Phnom Penh in 2000, the only time the event was held outside of Chinese soil.

This World Cup will miss the top-ranked European Tamara Boros, who usually regales audience with high-toss service and spectacular attacking game.

The Croatian withdrew from the tournament citing an injury and the first reserve player, Mihaela Steff of Romania, didn't accept the invitation for health reasons.

Austrian Liu Jia, ranked 21st, will hold European standard but isn't expected to go far in the tournament.

Liu shares the birthplace with Zhang Yining and Guo Yan. Singapore's Li Jia Wei, ranked seventh, is also from Beijing.

Li's first coach is her father Li Wanxiang, who had also trained Guo Yan.

Among the 16 World Cup participants, seven are former Chinese nationals or provincial team players.

The players who had switched their allegiances include No. 12-ranked Gao Jun, No. 50 Wang Chen, both of the United States, No. 4 Tie Yana and No. 13 Lin Ling, both playing for Hong Kong Special Administration Region, and New Zealand's Oceania champion Karen Li.

The World Cup also featured the world's top two defensive players - South Korea's Kim Kyung Ah and Belarus' Viktoria Pavlovich.

Doll-face Japanese Ai Fukuhara, who speaks impeccable Chinese and had played for the Chinese club Liaoning, enjoys as much popularity in China as in Japan. The 2008 Olympic prospect aims to lift from last World Cup's third place.

Lopsided games will be a regular fare in the group competition on Friday. African champion Osman Bacent of Egypt, ranked 375th, and Latin American winner Ligia Santos Silva, ranked 232nd, will be punching bags for the world-class players.