Halep leads their previous matches 4-3. She has won their last 4. Their last match was in May this year. She won easily on clay.
Halep started slowly against Osaka but seemed to have worked the youngsters game out after a few games. However Osaka took the opening set and was competitive in set 2.
Stosur had an excellent win over Safarova in the last round. She has had a good season on the clay so far. I think she can make a good match of this and value is on her at the start.
I feel Stosur could get into a winning position but I am not confident she can finish the job.
Back Halep if she is broken first.