If he was past his prime then, then he's past his prime now.
And if you're making the argument that Federer is a better player at the AO despite the fact that Nadal beat him in four sets last year in the semi (and other times before that), I'm gonna pull out the common sense card. No no, he's not.
I'm just saying God-mode Federer is greater than God-mode Nadal at the Australian Open. It's just that Federer doesn't bring it as often anymore. If he can against Djokovic at next year's AO, God help Djokovic.