They're all a bunch of bottlers as far as i'm concerned. Haye, Harrison, The Klitschkos, Mayweather, Pacquiao.. too concerned with money and the impact of losing a fight than they are about putting on good competitive fights for the fans.
This is why MMA is growing in popularity and boxing decreasing. In boxing, you handpick your opponents in hope of preserving an 'undefeated' record (dodging difficult fights or taking them when the time is 'right'). In MMA, guys just go out there and fight, and there's not such a taboo on losing. Undefeated records mean little, especially if you haven't been having tough fights. All the champions have lost at one point in their careers, and they come back from it to become better fighters.