After Serena Williams, Venus Williams also withdrew out from next week's WTA tournament in Montreal due to a nagging left knee injury.

In a statement issued by tournament officials Venus said:

"I regret not being able to play in Montreal next week. I was very much looking forward to playing in Montreal for the first time, but the pain that I am experiencing in my knee has unfortunately not gone away. I appreciate the support of the tournament organizers and Montreal fans."

The sisters also withdrew from Cincinnati which means that they will both skip the two top tuneup events for the US Open, year's final Grand Slam tournament that begins August 30 in New York. The only remaining US Open tuneup event possible for either Williams sister would be at New Haven in the week before the US Open.

Venus, who hasn't played a singles match on tour since June 29, when she was upset in the Wimbledon quarterfinals by 82nd-ranked Tsvetana Pironkova, would have played in Montreal for the first time.

Venus Williams pulls out of Montreal