Yeah, a very strange occurence. Nunn was not a one-punch KO fighter and Kalambay wasn't the kind of fighter to be caught napping. And there was nothing wrong with his chin. Barkley tested it with some good shots and Kalambay took them well. But here... Well, anything can happen I suppose and sometimes it does.
I think Graham vs Nunn is an interesting match-up here. They're pretty similar. Two awkward soutpaw with speed and great natural instincts but sloppy styles. Nunn has the reach, but he didn't really utilise it that much. Graham moved more, but I don't think that will factor in that much either.