10 Reasons CM Punk Might Actually Succeed In UFC
5. Level Of Competition

This is a weird one, right? Really, doesn't the UFC have the best fighters in the world?
Well, of course, most of them anyway (lets not forget the few they don't have, like Marlon Moraes and Ben Askren). CM Punk likely won't be fighting any of those, however. If you're the UFC, having Punk lose once or twice to competition with far more experience than him isn't very profitable. Having him win a string of fights - then maybe hit a ceiling and take a loss or two - is a better return on the investment.
Lets go back to the Herschel Walker comparison. No one is claiming he beat top guys, but he beat a guy with a 4-1 record when Walker himself was just 1-0. That fighter, Scott Carson, finished his career at 4-2 with the Walker loss, but a 4-2 fighter still has a winning record, and that's more than can be said about a lot of the guys you'll find shuffling around the regional shows that make up the "minor leauges" of MMA.
That sort of competition level is likely to be what Punk gets. The UFC may very well sign someone with a good win loss level who actually is training with complete unknowns for Punk's debut - and Punk's training level will already have him on a higher level. In short, it will be a winnable fight that actually looks dangerous for Punk, and while anything can happen, he probably will win it thanks to smart booking.