Devil_666
Super Freak
because Cain beat the piss out of him their last fight.
And the fight they had before that JDS put Cain to sleep in the first round, a little over a minute in. Former champs always have a shorter road back to the title after their initial loss. If they lose that second shot (or even a fight before that i.e. if Cain would've lost to Bigfoot or if JDS would've lost to Hunt) THEN they lose their spot and the next person in line moves ahead.
But as it is, Werdum hasn't done anything to magically leap frog him ahead of JDS.
If he would've beat Overeem in SF he would've already fought for the title (the UFC offered Reem a title shot for his debut fight). But since he lost, he fell back a step. Overeem was next in line and got destroyed by Bigfoot who got the shot instead. JDS is next in line. Werdum is behind him now.
I don't favor rematches either (especially immediate rematches) but this one makes sense. They're 1-1 and both fights were one-sided victories with reasonable excuses as to why; Cain had a knee injury for the first fight and JDS literally got separated & divorced before/during the second fight.