I read an article a couple years ago, either on mmamania or bloodyelbow.com that broke down Joe Silva's match making where basically he has each division currently ranked fighters and he tries to match fighters streaks. Meaning rarely do they match a guy who just lost a fight against a guy who won his last.
They(UFC) try to match guys who are on losing streaks so they can justify cutting whoever loses, they match win streaks to justify title shots.
As far as CM Punk's opponent though, I have NO idea and they probably don't have much either as this situation doesn't fit what is described above.