The pressure is all on Djokovic to continue to produce.
Also, Rafa is smart to skip.
Yes, definitely smart. But they can't skip the Masters events...so both Djokovic and Nadal still have a difficult road ahead.
And yes, Djokovic is defending here. It will be interesting if it is a Djokovic-Federer final.
Last year Djokovic's return game was just too good and Federer didn't do enough.
I also think it didn't help Federer to have an easy draw:
R32 Somdev Devvarman (IND)  W 6-3, 6-3
R16 Marcel Granollers (ESP)  W 6-3, 6-4
Q Sergiy Stakhovsky (UKR)  W 6-3, 6-4
S Richard Gasquet (FRA)  W 6-2, 7-5
F Novak Djokovic (SRB) 3 L 3-6, 3-6
R32 Michael Llodra (FRA)  W 6-3, 6-3
R16 Feliciano Lopez (ESP)  W 6-3, 2-6, 6-4
Q Florian Mayer (GER)  W 7-5, 6-1
S Tomas Berdych (CZE)  W 6-7(5), 6-2, 4-2 RET
W Roger Federer (SUI)  W 6-3, 6-3
But with Murray and Tsonga added to the mix this year, anything can happen.