Even the most devoted Chinese sports fans would barely have recognized Zheng Jie and Yan Zi four years ago, but now, the duo even need bodyguards at their training camps.

Coming into the Games among the most popular of China's 639 Olympic athletes, the female tennis players are aiming to win both singles and doubles medals.

Regardless of whether they succeed or not, they have already chalked up a significant win by lifting tennis to national prominence.

In the past four years, since Li Ting and Sun Tiantian won China its first Olympic tennis gold medal in Athens, the sport has ridden an upward curve domestically and is now on track to enjoy the largest fan base in the world.

"You would never have expected such changes," said Chinese Tennis Association vice-president Gao Shenyang. "The tennis environment is unbelievable. We talk tennis, we play tennis and we have 1.3 billion fans who expect something from us. Ten years ago nobody would possibly have predicted this sport could grow so fast."

Fifteen years ago tennis simply wasn't an option for most Chinese.

Back then, Beijing had just 20 courts, and only the most luxurious shopping malls stocked rackets and balls and television audiences were minimal.

But now, as China's women's stars scale the rankings and hoist trophies, an increasingly sports-mad public is starting to take notice.

Beijing Television Station opted to broadcast the 2006 Wimbledon women's doubles' final, won by Zheng Jie and Yan Zi, rather than the FIFA World Cup final between Italy and France.

With more people watching, more will inevitably want to pick up a racket and try their hand.

According to figures released by the State General Administration of Sport, more than 2 million Chinese people play tennis twice or more times every week, with the number expected to reach 6 million in two years.

The administration also says that among people aged 15-25, tennis is the second most played sport behind basketball.

No wonder tennis courts rank among the hottest properties in Beijing. Although outdoor courts normally cost 50 yuan (US$6) an hour, more than 400 yuan (US$50) for indoor, demand is growing.

With this growing enthusiasm, ambitious parents, eager to produce the next Roger Federer or Maria Sharapova, are starting to spend big money on tennis education.

However, repeating Athens' gold-medal heroics will be no easy job because most of the world's top tennis players are set to launch their Olympic battles next week.

Li and Peng Shuai will contest the singles' event while Zheng and Yan will be joined by Sun, who will team up with Peng.

Zheng, who entered the Wimbledon Open final as a wild-card player last month, said the magic run gives her extra confidence to realize her Olympic dream.

"I had never thought I could do this well (at Wimbledon), but I am sure it is crucial for my preparation for the Games," she said. "After the August Olympics I might put in more effort on the singles, but as for the Beijing Games, my mind is still on the doubles.

"Everybody wants more medals, but I think my partner Yan Zi and I appear more hopeful in the women's doubles and we have been preparing for a long time."