I agree about the 'demeanor' comment. When he is at his best he is bolshy looking, head right up in parade ring, ears pricked, daring anything to look at him or get in his way. He is known to bite at home, just very playful. And altho he makes some howlers he throws himself at his fences with joy, and confidence. For some of last season (or maybe even all of) he never looked confident and his body language was lack lustre. I've no idea if he was injured, have never heard this, but he had far less sparkle than the horse who won the Tingle Creek as a 5 year old. He also seemed to get thinner and thinner as the season wore on and his coat did not look that great either.
He did have a long and hard season the year before, he did so much, and as Paul has said in his column, Denman is much more lightly raced than Kauto, so who knows, perhaps he was just in need of a rest.
When he was last paraded he looked back to himself, was messing about, pawing the ground, pulling his lassses arms out and looked lean and mean. Fingers crossed that he is well now and has regained his lust for life!
Personally I also do not think Cheltenham suits him, or at least not the Gold Cup. King George is much more his thing.