Imagine the scenerio of Haye winning a close, but unanimous decision and Harrison has his moments along the way, or Harrison susses out Haye and pulls away before meeting a round 12 Hayemaker which ends the match. Both are nightmare scenarios
It's not very likely though is it? IMO Harrison's best chance at winning is to try and do to Haye what he did to Williams in the second fight. I imagine he's just going to look like a rabbit in the headlights once he gets in the ring, I think all his talking is just whistling in the dark. Haye's going to batter him.
If Haye doesnt get him out in the first 3 rounds Harrison's confidence will grow at the same time as Haye's stamina might falter...
The Valuev fight was different though. Valuev was not some hive of activity that Haye had to worry about and struggle to cope with, he just walked forward, jabbing. Haye really didnt have much to worry about, If Valuev had been throwing volume it would have been more difficult. Problem for Harrison is the fact he's gunshy, his best tactic would be to weather the early storm and then really attack Haye after 6 rounds or so.
