Yeah -- Fed has more points to defend in March and April than Djoko, I think. Seems that way.
Nole defends only Miami, while Fed defends Rotterdam, Dubai and Indian Wells, after which Nole defends runner-ups at MC and Rome, while Fed defends Madrid; NOle defends RG runner up, but Fed defends Wimbledon champion, also the Olympic points drop completely.
I think Fed would need some kind of superhuman effort to get back to #1 this year, to play like it's 2006 again, no way that happens. The only half-chance to hurt Nole was here and that's gone now. Rafa is way behind and has to defend 4500 points on clay/pretty much everything, I don't see him doing it either.
Murray is the only one who has some kind of chance if he really tears it up before Wimbledon, but he never did that great on clay, it would need a small miracle + shaky Rafa
Bottom line, I think Nole is almost sure to get to 100 weeks at #1, after that who knows what can happen