Serena Williams out of China Open with injury

BEIJING (AP) — Defending champion Serena Williams has pulled out of the China Open with a left knee injury.

The top-ranked Williams had been due to face Australian Samantha Stosur in the quarterfinals on Friday.

Playing with strapping on her knee, the American beat Lucie Safarova 6-1, 1-6, 6-2 in the third round Thursday evening and then skipped her post-match press conference because of swelling in the knee.

Williams retired from the Wuhan Open a week ago during her first-round match with a viral illness. Her sister, Venus, also withdrew from the China Open this week, citing a virus.