Getting in shape isn't the issue, getting the matches under your belt is.. Not sure how you can say 2009 would ultimately be harder.. He had zero confidence against top players from August 2009 to April 2010... He had an extremely poor and obscure stat for his standards against top 10 players in that stretch. I mean he lost to Ljubicic and Roddick in IW/Miami after being up a set in each match, he lost to Davydenko after being up a set and serving for a match twice (?) if I remember correctly, he lost to Djokovic, Davydenko and Del Potro 3 times in a row each. If he struggled that bad, I sincerely doubt it will be easier for him this time around when he has ONLY gotten older and arguably slower.
One big win is all it takes to gain back that confidence. As I said, starting to play from the beginning of the season, when almost all the players come back after two months without matches, should make things easier. He seems pretty confident in interviews and if he feels 100% phisically and is able to practice as much as he wants, then I don't think this confidence thing should be such a big issue. Losing matches after winning the first set or getting broken when serving for the match has become a habit in the past two years, so those 2010 loses don't seem that strange anymore.