Sam Stosur: "I didn't play aggressive enough"

US Open champion Sam Stosur has been critical of her performance against Victoria Azarenka earlier today.

Stosur, 27, rarely threatened her opponent from Belarus, eventually slumping to a 6-2 6-2 defeat in Istanbul.

After the match, Stosur revealed that she was far from satisfied with her display.

"I didn't play aggressive enough. I don't feel like I did anything," she told reporters.

"I just kind of got pushed around the court and, eventually, was made to make an error or she'd hit a winner."

Stosur must now defeat Li Na in her final group match to stand any chance of progressing to the semi-finals.