DOHA, Oct. 30 (Xinhua) -- Serbian Jelena Jankovic downed Caroline Wozniacki of Denmark and American Venus Williams did not hit a ball, but all of the three reached the semi-finals of the WTA Championships here on Friday.

    After the withdrawal of both Dinara Safina and Vera Zvonareva, the semifinalists from the two groups of four became permutations, following the first ticket secured by Serena Williams on Thursday.

    Despite her defeat, Wozniacki still survived for the weekend after Belarussian Victoria Azarenka retired injured in the third set of her match against stand-in Agnieszka Radwanska of Poland.

    In Saturday's semi-finals, world number one Serena will face White Group runner-up Wozniacki while her sister Venus, who is through despite two defeats in three matches in the Maroon Group, plays Jankovic.

    Venus only made the last four on a sets count back after already-eliminated Svetlana Kuznetsova beat fellow Russian Elena Dementieva 6-3 and 6-2 to leave three players tied on one win each.