What is worrisome for Djokovic fans is his body breaking down. Even in this 4 set win, he was having physical problems. If the match had went 5 sets - I have no idea who would have won. Last year at the end of the season he was toast at the Year-End master's .... Sure, he's improved in his fitness but I think he has a long way to go because the tennis season is such a long season. I was concerned for him at the beginning of this year when he played Hopman cup. He just doesn't seem to hold up (bodywise) in a lot of tournaments. In fact, I wasn't surprised when he called for a trainer in this match.
So...all that to say is it'll be hard for him to pick up points in the clay season because Nadal has proven that he can and has defended is clay points so I don't think Djokovic can pick up a lot from there. Then Wimbledon is so hugh for Roger that he'll throw everything in the wind to win that one. (And remember Djokovic had to default in that tournament because he was tired). Wimbledon can play like that a lot - a lot of matches get backed up, etc.
Djokovic got hot through the US Open series so he'll have to defend these points, which he may. But Djokovic's fans have to have been alarmed at how he finished up the Master's Cup. He didn't have anything left. Now maybe he will manage his schedule a little better this year because, again, he was toast at the end of last year.
All this to say - heck, who knows where he'll finish! If only we all could call the future, we'd all be rich!