Williams pulls out in LA
Serena Williams is the latest withdrawl from the Los Angeles Classic and her knee injury will be a concern ahead of the US Open.
The younger Williams sister has followed her sibling, Venus, world number four Svetlana Kuznetsova and former world number one Lindsay Davenport in pulling out of the LA tournament - all four are struggling with knee injuries.
It is a real concern for Wimbledon runner-up Serena, having been forced to pull out of the semi-finals at last week's Stanford event and with just over a month to go until the US Open.
Russia's Anna Chakvetadze was impressive in reaching the third round in California, with a crushing 6-1 6-1 victory over Marta Domachowska.
There was disappointment though for sixth seed Daniela Hantuchova, who has only just returned from a foot problem.
The Slovakian was beaten 6-2 6-4 by Olga Govortsova of Belarus in her second round match.