Overeem needs to knock Cain out in the first 60 seconds else he will gas even harder than JDS did. Werdum has a decent shot of submitting Cain if he can get it to the ground, but I see Cain working Werdum up against the cage until he gasses.
Agreed, Reem's cardio is more questionable than JDS'. Also Reem was out struck by Werdum, and Werdum is no Cain in that department so that's something to consider.
I have Cain taking this one in convincing fashion even though Reem is proven on his back, he's spent a lot of time there getting concussed by light heavyweights.