Clijsters makes shock withdrawal from Rogers Cup

Kim Clijsters may be a doubt for the US Open after a stomach injury forced her out of this week's Rogers Cup.

The Belgian was the second seed in Toronto and competing for the first time since the French Open but she was forced to retire barely an hour into her opening match. Clijsters was leading China's former Aussie Open semi-finalist Zheng Jie 6-3, 1-2 when she called it quits, clearly in some discomfort and she revealed afterwards that she had felt the onset of the injury during the warm-up.

Clijsters had it taped and attempted to play through it but after a season already severely disrupted by injury, she may live to regret that decision. The Belgian won the Australian Open in January but her run of misfortune began in April as she injured her ankle before shoulder and wrist injuries kept her out for much of the clay-court season. A foot problem forced her out of Wimbledon, the tournament she desires to win most and she will be gutted if she is not fit to defend her crown at Flushing Meadows.

"During the match it just felt like it went worse," she said afterwards. "I already had an ultrasound here on site and I have a partial tear in my left stomach muscle and a little bit of blood."

Caroline Wozniacki's shock defeat earlier today has left the tournament without its top two seeds after just two rounds but the in form Serena Williams looks to be going strong.