ESPN Tennis

MONTREAL -- Justine Henin-Hardenne added to the growing list of former Grand Slam champions who are skipping next week's Rogers Cup.

Henin-Hardenne announced her withdrawl Thursday due to a knee injury. The Belgian joined France's Amelie Mauresmo and American Venus Williams, who announced Wednesday that they would not be participating.

"I am really disappointed to have to withdraw from the Rogers Cup, which I have been preparing hard for over the past weeks," said Henin-Hardenne, a finalist here last year. "Unfortunately, my right knee has not fully recovered and my doctors have told me that I need to rest it for a few days. I am going to be doing everything I can to get back on court as soon as possible."

Henin-Hardenne has not played since reaching the final at Wimbledon in July, where she lost to Mauresmo. The two-time defending French Open champion has won five Grand Slams in her career.

The defending champion is Kim Clijsters of Belgium, who pulled out of this week's tournament in Carson, Calif., but is still scheduled to defend her title.

The $1.34 million hardcourt tournament begins Monday and is part of the U.S. Open Series culminating with the U.S. Open -- the final Grand Slam of the season -- later this month. Henin-Hardenne won the U.S. Open in 2003.

"The players list we received in July was at least as strong as any Grand Slams," Rogers Cup director Eugene Lapierre said. "Even with the loss of Henin-Hardenne, the group of players commited to play in Montreal is more impressive than in most other WTA Tour Tier I events."

The list was a lot more impressive before Wednesday, when Mauresmo and Williams pulled out. Mauresmo won both Wimbledon and the Australian Open earlier this year and Williams is a five-time Grand Slam winner, most recently at Wimbledon a year ago.

Also withdrawing Wednesday was Russian Elena Bovina, who has not played in over a year due to injury but was planning a return at this event.