See Iran Barkley v Hearns I and tell me you dont believe it! [ame]http://www.youtube.com/watch?v=iopkeD-B7Qs&NR=1[/ame]
There is ALWAYS a punchers chance, but depending on the styl match up and the level disparity that "punchers Chance" will diminish with regard to how likely it could happen. Look at Andrade vs Bute.....look at Taylor vs Froch. It happens all the time. And in boxing anything can happen with one punch. If you got that power that is the great equalizer.