You can have a bad day, or you can be a crappy fighter all along and get exposed. Kimbo was the latter.
I'm not sure I agree with Kimbo being written off because of the Seth Petruzelli knockout. Anyone can have a bad day, there are a thousand variables to each and every blow, Kimbo might have just caught a bad break on that one.
You should watch the video of his fight with Sean Gannon.
Look, I'm not advocating Kimbo, or saying he'll be a dominant force in the season of TUF - I'm only noting that the Petruzelli knockout is thus far an isolated incident on Kimbo's record and has yet to be proven a consistantly fatal flaw.
I did an old piece well before the Petruzelli knockout called "Ten Ways to Beat Kimbo Slice" that focused on the enormous number of flaws in his fights with Mercer and (particularly) Thompson.
Frankly, I've always thought Teddy Atlas' line "boxers are made, but punchers are born" was a pretty true statement.
That said, the guy's got a lot of raw talent going for him. Watching his first street fights, any fighter worth his salt can see by the way he pivots, springs and throws punches that Kimbo has a ton of natural talent. Kinetics that are nearly impossible to learn in a gym, but come easy to the right body. All in all, I'm not counting him out for a single moment of weakness until that 'single moment' becomes a reoccuring theme.
Kimbo is a puncher. That's fine.
Be has no head movement. He has no understanding of how to effectively work the lower body in a way that allows him to throw kicks and knees. He has no understanding of how to work in the clinch (which is especially apparent in the Sean Gannon fight). He has no ground game to speak of (I mean, his technical skills rival those of James Thompson, which sort of speaks for itself). And now, we learned from the Petruzelli fight, that he can get knocked out by a lightheavyweight.