<div><p>Defending champion Venus Williams reached the semi-finals of the WTA Championships without hitting a ball on Friday as organisers avoided potential embarrassment over the event's scoring system.</p><p>Williams reached the last four - along with Jelena Jankovic and Caroline Wozniacki - despite losing two of her three group matches.</p><p>The American was assured of joining sister Serena in the semi-finals when Svetlana Kuznetsova defeated Elena Dementieva 6-3, 6-2 in the concluding Maroon Group match.</p><p>On Saturday, Serena will face Wozniacki while Venus tackles Jankovic for places in the final of the 4.55 million dollar tournament.</p><p>Under a complicated qualifying system, Venus pipped Dementieva for a last four place despite both players having a win apiece and with the Russian having defeated the American when they met on Tuesday.</p><p>However, Venus went through having won more sets.</p><p>In the White Group, Jankovic also made the last four, comfortably defeating US Open runner-up Wozniacki 6-2, 6-2.</p><p>Wozniacki then faced the possibility of being eliminated from the tournament despite having two wins.</p><p>However, the blonde Dane was saved when Victoria Azarenka was forced to retire injured against Polish replacement player Agnieszka Radwanska.</p><p> Azarenka had led 6-4, 5-2 before becoming severely restricted by a right thigh and back injury which needed constant attention.</p><p>She was eventually forced to quit in floods of tears in an echo of Wozniacki's injury-hit win over Vera Zvonareva the day before.</p><p>Radwanska, who had in turn replaced an injured Zvonareva, was leading 4-1 in the final set when the Belarussian hobbled away.</p><p>Jankovic came into her match far fresher than 19-year-old Wozniacki, the world number four.</p><p>The 24-year-old Serbian had spent just 95 minutes in total on court in two matches after Dinara Safina withdrew through injury from her second tie after only 12 minutes.</p><p>In dramatic contrast, Wozniacki needed 5hr 48min to see off Azarenka and then Zvonareva, only surviving the clash with the Russian after overcoming a crippling attack of cramps.</p><p>"I didn't have anything left," said Wozniacki, who again played with her left thigh tightly-strapped and appeared at her news conference with her leg and stomach iced.</p><p>"I couldn't play like I wanted to. I had some pain in my stomach muscle, as well, so I couldn't serve. I feel like I deserve to get to the semi-finals."</p><p>For Jankovic, who made the season-ending championships as the eighth and last qualifier, it was a third win in three career matches against the Dane.</p><p>"I wanted to reach the semi-finals and I didn't want to get into long rallies with Caroline," said Jankovic, who admitted she had let herself down in her opening defeat to Azarenka.</p><p>"I only arrived on Sunday from Moscow where it was very cold and here it's very hot. It takes time to get used to the conditions. It was a bad day against Victoria.</p><p>"But in tournaments like these it's important how you finish, not how you start."</p><img src="http://admatch-syndication.mochila.com/images/ad.gif?aid=62324634&bid=informcom" /></div><div id="copyright"><div>

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