Stosur won their only previous meeting. That was in May 2014 on clay. She won in 3 sets.
Muguruza has dropped just 1 set so far. That was in the first round match with Schmiedlova. She dealt well with Rogers in the last round although having been broken in the opening game she left it very late to break back. Rogers was broken serving for the set and was then broken again as Muguruza took it 7-5.
Stosur has also done well but has been helped by the heavy conditions. The rain changed the playing conditions and favoured big hitters. She was struggling a little against Halep but after the rain delays she adapted better. Halep was broken serving for the opening set and didn’t win a single point in the tie break. I was surprised that Stosur’s match with Pironkova was so close but she never does things the easy way.
I have to go with Muguruza today as she can play in “normal” French Open conditions and can also hit big if they get affected by rain. Three sets seem likely. She starts too low at around 1.35 and value is on Stosur at the start.
Back Muguruza if she is broken first.