World tennis number two Kim Clijsters has withdrawn from her opening match at the Rogers Cup in Canada with a partial tear of her left stomach muscle, casting doubt on whether she will be fit for this month's US Open.
The tournament's second seed said her left stomach muscle felt tight during her warmup earlier in the day and had the area taped in a bid to protect the muscle.
There were routine second round victories for Serbia's Ana Ivanovic, German Andrea Petkovic, American Serena Williams, Li Na of China, Australia's Samantha Stosur, Poland's Agnieszka Radwanska and Francesca Schiavone of Italy.
