Toronto, Canada (AHN) - Venus Williams withdrew from the Rogers Cup for undisclosed reasons on Tuesday.

Williams, who won her fourth Wimbledon title last month, fell in the quarterfinals of her next tournament appearance in San Diego, losing to Anna Chakvetadze of Russia 6-7, 7-6, 6-2.

Williams still moved up to a No. 14 ranking in the world, despite the setback.

Top-ranked Justine Henin and No. 2 Maria Sharapova are still slated to compete in the tournament that opens Monday. Amelie Mauresmo withdrew earlier this week, however, and officials are concerned that more top players could follow suit as was the case last year.