Kerber. Sveta had her issues with the heat today and she's played like 6 matches in the last 7 days (according to the commentator during the Woz match). Plus Kerber matches up well against hard hitters and she's got good passing shots (unlike Wozniacki today).
Of course Kuznetsova could turn in a brilliant performance and blow Ang off the court but I'm not feeling it. Kerber in 2.