Victoria Azarenka and Maria Sharapova head the field for the WTA hardcourt tournament that starts on Monday with Serena Williams lurking dangerously as her injury comeback continues. Eight of the world's top 20 will take part in the WTA Tour's first premier level tournament since Wimbledon, which marks the start of the women's build-up on American hardcourts to the US Open. Belarusian Azarenka and Russian Sharapova, ranked four and five in the world, are the top two seeds. They'll be vying to reprise their meeting in the final last year, when Azarenka triumphed for the title. Both arrive in northern California fresh from strong runs at Wimbledon, where Sharapova fell in the final to Petra Kvitova but said her first appearance in seven years