WTA: Serena pulls out of clash with Russian hopeful

Anna Chakvetadze's hopes of making the semi-finals of the Sony Eriksson WTA Championships remain alive after opponent Serena Williams was forced to pull out of their clash on Wednesday.

The American began to slow up midway through the opening set and then retired to receive treatment on her left knee.

Chakvetadze now needs to beat Jelena Jankovic to make the semis, while Williams’ ongoing participation in Madrid is far from certain.

Justine Henin has made it through already from that group by beating Jankovic and after Williams’ withdrawal qualifies for semi-finals automatically.

Chakvetadze and Jankovic are contesting the second qualifying berth from the yellow group.