Samantha Stosur

BEIJING: World number one Serena Williams pulled out of the China Open hours before her quarter-final against Sam Stosur on Friday because of an injury to her left knee, the WTA said.

NEW YORK: Wimbledon champion Petra Kvitova and runner-up Eugenie Bouchard launched their U.S. Open campaigns with a bang, blasting by their respective first-round opponents in quick fashion on Tuesday.