If Nadal said this and meant that he could win this, then all I can say that it would be a miracle and all the other participants would have to be suffering from injury or they were ill. No one could come back from six months off and play well enough to win. I really don't think we will see Nadal winning until he's back on the clay and even then I still have my doubts it the early clay season, but we will have to wait and see. It took Del Po an age to get back to winning ways.
I'd be very surprised if Nadal was back to winning ways immediately. To me his recent comments sound like an attempt to be ultra positive, which I suppose is good in some ways, but might not be realistic. Still, Abu Dhabi is only an exhibition, so I suppose it is academic anyway.
I think with Delpo his injury affected his confidence and that took him a while to get over. He was out for a year though, maybe even a bit longer, so it is bound to shake you up a bit when you get back. It will be interesting to see when or even if, Nadal can get back to his best.