I really don't understand what his problem on clay is. He has a game to be a very good clay player, yet somehow he is just clueless on clay. and forget about #1, I don't think he is getting there anytime soon. Nole is simply too solid on all surfaces. I think Nadal is more likely to get back to #1 at some point.
He doesn't construct points very well, he's generally either entirely defensive or all out attack. And even when he's all out attack he finds it hard to hit winners and on clay you need to be able to hit through opponents.