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To make the final of the Australian Open, Li Na's challenge was to take out both the Williams sisters in rapid succession.

She had a heroic crack at it to the point where a few shockwaves might have shuddered through the women's locker room. If this is a sign of things to come now that the Chinese revolution has been formally recognized -- Li and Zheng Jie provided their nation with two Grand Slam semifinalists for the first time -- then the message is unmissable: Be alarmed.

Zheng's one-game capitulation to Justine Henin added an ambiguous note to that, but it shouldn't be forgotten she fought back from a set down in each of her first three matches. She has contributed her share to a historic week. In coming from behind to beat Venus in three rigorous sets and then taking Serena to two desperately fought tiebreakers yesterday, Li demonstrated not only that she can seriously play but has an impressive ticker.

In any sporting environment, that adds up to serious trouble for the opposition and so it proved for the American superstars. Taking each of them down in the same tournament is probably the sport's toughest task. It's only been done once at the Australian Open (by Martina Hingis nine years ago), while Arantxa Sanchez-Vicario, Steffi Graf, Kim Clijsters (twice), Lindsay Davenport and Justine Henin have managed it elsewhere.

In other words, if you're not a world No. 1 -- a superstar yourself -- forget it. But obviously nobody told Li that.

As had been the case against Venus, she got off to a shaky start, dropping serve in the first game. Unfazed, she refused to be stared down by her vastly more accomplished opponent, never more so than when she saved three match points on serve in a riveting 11th game of the second set. A fourth match point came two games later. By then the quality of the tennis was riveting.

Serena was not surprised. Asked the previous night what she expected, she said: "You know, she's a fighter. I have to be ready." Correct. The crowd warmed to the same message -- that this was a classic case of an established champion up against a determined and talented challenger, the dilemma being whom to support.

In Australia, that is usually the underdog. Li sensed it, saying she felt the fans were on Serena's side at first but when they saw how hard she was fighting, the mood changed.

It's fair to suggest Australians aren't used to barracking on behalf of Chinese sportsmen. We don't see many. But Li -- and Zheng, for that matter -- were a welcome exception.

Li is more than a very good tennis player. She is an engaging ambassador for the more worldly, less secretive image China has been keen to promote either side of the Beijing Olympics. Although her English remains fractured, she has been a hit in the media room, joking with the international press -- she told one aging, balding reporter he should follow her lead after he asked how often she changed her hair color -- and providing honest answers on mildly sensitive subjects. She even threatened to "maybe take the beer" to celebrate her quarterfinal win.

Li's trademark smile never faded, even in defeat. Asked if she was disappointed, she said: "Not so bad -- good day for my tennis."

Good day for all tennis, actually.