"But after the tests this morning, for the first time in a while, they were able to give me a different answer and a different problem.

"But on the other hand this is something that needs a lot of time to heal, which really hurts me to say that I have to miss the Olympics."

Playing her first match since a shock second-round defeat by compatriot Alla Kudryavtseva at Wimbledon in June, Sharapova twice received treatment on her shoulder during her three-hour battle with Domachowska in Montreal on Wednesday.

While her groundstrokes were crisp and powerful the Australian Open champion struggled with her serve, committing 17 double faults.

Sharapova said her shoulder had been troubling her since she played at Indian Wells, California in March.

After the results of tests in Montreal, the Russian was flying straight to New York to have the injury examined by sports physician Dr David Alchek, who will provide a second opinion and advise her on how much time she should take off.