Kerber leads their previous matches 4-3. Their last one was on October last year in Hong Kong. Kerber won in straight sets on a hard court. She has won 3 of their last 4 matches. Stosur won on clay in 2015.
Kerber played a strong match to beat Bouchard in the last round. Bouchard had done well in the previous round and put up a good fight but only broke Kerber once.
Stosur was also impressive in the last round against Doi who I had expected to give her more trouble than she did. She was also broken just once.
Back Kerber if she is broken first. She could probably win this playing at 75% of her best. Stosur needs to be at her very best or for Kerber to have a poor day for her to take it.