1. About the serve
After watching Tokyo final and realise that he only won 35% of his first serve. I believe Nadal is really thinking about his serve. His serve maybe good enough to win most players, but not for players who really good in return game this year.
Us open 2011 Final
1st set 40% winning of first serve 35% winning of second serve
2nd set 54% winning of first serve 29% winning of second serve
3rd set 61% winning of first serve 53% winning of second serve (it is higher than Djokovic and Nadal eventually won this set)
4th set 44% winning of first serve 40% winning of second serve (Djokovic with 71% and 75%)
Wimbledon open 2011 final
1st set 77% winning of first serve 20% winning of second serve (But Djokovic got higher, 82% and 67%)
2nd set 46% winning of first serve 33% winning of second serve (Djokovic maintain at 88% and 50%)
3rd set 93% winning of first serve 75% winning of second serve (Djokovic dropped to 55% and 38%)
4th set 47% winning of first serve 50% winning of second serve (Djokovic improved to 64% and 60%)
Montreal 2011 Round 2
1st set I remember Nadal won 80-90% on his 1st serve aginst Dodig.
2nd set 82% winning of first serve 55% winning of second serve, but only had 44% 1st serve in. (Dodig 71% and 67% and 62% first serve in )
No statistic for 3nd set, but whole match he played better than Dodid in term of statistic except Dodig had 19 aces.
Cincinnatic 2011 QF
Nadal serve double faults under break point.
2010 US open, Nadal served pretty well, one of best performances of his serve.
2. DND tactic (Copyright by Davydenko, Nalbandian and Djokovic).
I still believe Nadal needs to change his game as many other people already said. His movement already slow down. Try flat out the ball and give more deep slice to win more time to recover. His groundstroke needs to be always deep. More people will use same or similar tactic when they against Nadal, keeping Nadal cover a lot of ground.
3. Youngsters in 2012
As some talented youngsters start to show off, everybody will face challenges from new generation.
If Nadal can cover first two issues, I expect he will French Open and Wimbledon.
If he can't, I expect he win French Open only.