Serena's power is too much for any of them to deal with bar Azarenka and even Azarenka is relying on errors to get into the match. Radwanska's great but there's a glass ceiling that she can't excel past because of her lack of power to make winners.
Wouldn't call Azarenka winning a shock. Maybe anyone but her and Serena. Anyone other than Azarenka beating Serena I'd call a shock though. It'd probably involve Serena imploding though.
It's more to do with her confidence and form. If she loses here then i don't see her doing anything in melbourne. If she has a good run and gains some confidence then she has a better chance in doing well at AO.