Mauresmo, who lost in the third round of last week's German Open in Berlin after returning from a two-month layoff due to appendicitis, struggled to find her rhythm against the Australian, who hit out aggressively.
Mauresmo had two match points in the deciding set but slid to another unexpected defeat when she netted a backhand
"When you are out for a while you just want to get back to your level as quickly as possible and obviously it's not there yet," the Frenchwoman, who won the title in 2004 and 2005, said after toiling for more than 2-1/2 hours.
"I guess I didn't keep the intensity the way I should have. I didn't take my chances, so I don't have much to say. I'm just disappointed. The lack of matches is showing a bit at the moment."
