Djokovic downs Dimitrov, ailing Williams withdraws

World No 1 Novak Djokovic continued his march to a fifth China Open title by dismantling a flat Grigor Dimitrov in a one-sided quarterfinal on Friday after women's top seed Serena Williams was forced to pull out through injury.

Briton Andy Murray will face Djokovic in the last four after also storming through with a 6-1, 6-4 win over US Open champion Marin Cilic, while Maria Sharapova destroyed Svetlana Kuznetsova in an all-Russian women's quarterfinal.

American world No 1 Williams, who had reached the last eight on the Beijing hard courts after a 6-1, 1-6, 6-2 win over Czech Lucie Safarova late on Thursday, cited a problem in her left knee for handing a walkover to Australian Sam Stosur.