Maria Sharapova, shown here playing a singles match against Kim Clijsters on Sunday in Cincinnati, later withdrew from this week's Rogers Cup in Montreal because of a heel injury. (Ronald Martinez/Getty Images)

Russian tennis star Maria Sharapova has withdrawn from the Rogers Cup tennis tournament for the second time in three years.

The three-time Grand Slam champion and 2009 Rogers Cup finalist made the announcement Sunday after injuring her left heel in a 2-6, 7-6, 6-2 loss to Kim Clijsters in the final of a WTAS event in Cincinnati.

"I felt some pain in my foot late in the second set which kind of scared me, so I have been forced to pull out of Montreal. I am hoping I just need a few days of rest."

The $2-million tournament will be missing other big names when action begins Monday.

Heavy favourite Venus Williams withdrew from the tournament on Friday due to a lingering knee injury, joining a list that includes her sister Serena. The world No. 1 is recovering from foot surgery.

Fifth-ranked Samantha Stosur of Australia recently pulled out with a right arm injury, while seven-time Grand Slam champion Justine Henin won't be in Montreal because of an elbow problem.

Sharapova was seeded 12th for the Montreal event and was scheduled to play Lucie Safarova of the Czech Republic in an opening-round match at Uniprix Stadium.

In 2008, Sharapova won her first-round match against Poland's Marta Domachowska and then withdrew from the tournament because of a right shoulder injury.

Injuries have wreaked havoc on the former No. 1 player in the world. Since winning the Australian Open two years ago, Sharapova has been slow to return as an elite player.