(CNN) -- Defending champion Venus Williams reached the semifinals of the $4.55 million WTA Championships in Qatar on Friday without hitting a ball
The American, who lost two of her three group matches, joined sister Serena in the last four after Svetlana Kuznetsova had defeated Elena Dementieva 6-3 6-2 in the concluding Maroon Group match.
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.
However, Venus went through to the last four having won more sets over her three outings.
In the White Group, Jelena Jankovic, who made the semifinals in 2008 just before her elevation to the world number one spot, also made the last four, comfortably defeating U.S. Open runner-up Caroline Wozniacki 6-2 6-2.
Jankovic came into her match far fresher than her teenage opponent, the world number four. The 24-year-old Serb, defeated in her opener by Victoria Azarenka, had spent just 95 minutes in total on court in two matches after Dinara Safina withdrew through injury after only 12 minutes of her second match.
In dramatic contrast, Wozniacki needed nearly six hours to see off Azarenka and then Vera Zvonareva, only surviving the clash with the Russian after overcoming an attack of cramps.
However, Wozniacki still reached the last four after Poland's Agnieszka Radwanska, who replaced the injured Zvonareva, beat her best friend Azarenka, who was also forced to quit while trailing 4-6 7-5 4-1.
A clearly fatigued Wozniacki will now face new world number one Serena in Saturday's semifinals, while Jankovic will fancy her chances of overturning an out-of-sorts Venus in the other semi.