I think that people had dramatised a lot about Nadal's physical condition. Nadal trained on August (http://www.youtube.com/watch?feature...&v=2Mc1uZAzS3U
), trying to go to the US OPEN. His knee has been a problem always. He decided not to go to the US OPEN, and after that he stopped training. He knows the feeling of playing and practising with pain on his body. He has done it before. But now this injury was a little bit different and more important, but he always know that was only a matter of time (he had some years ago a more important problem with one foot that put on risk his career).
In fact, I think that he was able to play on Abu Dhabi and Doha. And when I say that he was able, I say that you put Nadal in a court and he plays an acceptable first match. But Nadal wants more than play one acceptable match (and maybe win) if he knows that he can't reach, for example, the quarterfinals. But the problem with Nadal's condition is about Nadal's mental condition. He hasn't played in a long time, and he is a player that depends a lot of being fit to play a high level tennis. He has to gain confidence and recover all the feelings on court. He is not coming back to make Australian Open R16, for example. He is coming back to be 'competitive'. Nadal says lots of times the word 'competitive'. He means that being 'competitive' is being able to play his best tennis in order to have possibilities to win matches. To do all he can do in order to win, and then if he loses is because the other player played better and not more, not because he wasn't fine. For example, after Australian Open 2012 final he said that he was happy because he felt that he was competitive against Djokovic (after a 2011 with lot of loses, where he only felt competitive on the 3rd set of the US OPEN 2011 final).
If we think about Nadal's return with lot of care, it is not a good decision to come back in the Australian Open. Hot temperatures (reaching 40 degrees) and long matches played on five sets. He can return on Acapulco or before (on a South American clay tournament) and he can have his first feelings on court on his best surface and against players that are not a serious problem for him. Another question was: if I come back on Doha / Australian Open, what would happen if the knee is another time a problem? Starting to play on clay is better for him to defeat his fears.
I've not doubt that he'll play most of the tournaments that he played before. Cotorro, his doctor, said on an interview that this type of knee injury doesn't have to come back. Nadal always will have problems with his knees, but maybe problems less serious, like injuries that he had before. Nadal environment said on July/August that they will try to play more on clay and less on hard, but Toni Nadal said more than one time on radio interviews that with this ATP calendar they don't have lot of chances to make their own calendar, so Nadal will play almost the same tournaments that he has played before. If he is going to be as competitive as last years on other courts than clay (and grass too) is the real unknown thing.