Kerber is ranked higher though. It's likely Kerber won't even play unless either Sabine or Julia have a really bad match on the first day and Rittner chooses her to play a singles match on the second day instead. If it came down to the doubles, it'll definitely be Julia-ALG playing that.
my impression was that German Tennis Fed doesn't like Kerber.
and didn't Kerber threaten to play for Poland?
But that was before she had her epic USO run last year