It looks like Haye is going to box cleverer and take it longer. That is a smart strategy for him, as on boxing skill he is more dangerous than Bellew with a longer reach. If he gasses himself early, lets Bellew avoid him he sort of plays to Bellew's approach. So it will be interesting to see if he can jab and move, build up a solid points advantage and look for a knockout later in the fight.
The elephant in the room is as always the fitness. He has 8 rounds without injury in 6 years. Before the last Bellew fight he had 3 rounds in 5 years. As others have touched upon, you can build up general fitness but there is something unique about ring fitness. We have also seen his achilles damaged and his bicep done, as well as question marks over his shoulder. These difficulties are more likely to play out than last year.
There's no doubt he looks to have trained properly for this fight, but at 37/38, with an injury riddled body having not been treated properly for several years there are some doubts as to whether a 12 week camp can prepare him to go long. To me that is what this fight will depend on. Can his body hold up? Can he keep throwing shots for 8 or 9 rounds?
It's a compliment to Bellew he isn't just going to blast him out in 2. My own belief is, Bellew his harder than he expected last time, and was much more astute and quick in defence than he thought. Underneath some of the jack the lad idiocy Bellew is a very smart boxer and Caldwell is nobody's fool. They will likely recognise their key to victory is making Haye miss and forcing him to take ever more ambitious shots if he begins to tire. He's a canny fighter, I suspect may come in slightly lighter and will be better prepared for this fight as he knows he can take Haye's best shots and deflect them.
I do think Bellew is better in this fight. The confidence you get from beating someone is enormous. From taking their best shots. I also think he will be happier to box his own fight, as I said above suspect he will be lighter and fight it more as a big cruiserweight. It's odd really but I think rounds 1-6 he is flawless. He was only behind by 1 on the card. He makes a mess of rounds 7-11, gassed himself out and ignored the advice of his coach of just box and moving before going for the finish around the 8th/9th round and got caught up in the emotion. If he can take Haye late and make him miss I suspect he will be more clinical than last time. Yes he doesn't have a big shot to end it, but he can put together a sequence of punches that can get a stoppage.
Despite what David Haye says, I think his best chance will be to finish it early. If Bellew gets through to round 5, then he starts to become the favourite, as whatever preparations Haye has done, I don't think he can alter the sort of fighter he is at his age, which is an explosive knockout merchant.