I'm rooting for Cain 150%, but I don't think there's a guy in MMA who Brock won't eventually get a hold of and get on top of. I think this is going to happen eventually during the fight, and I don't think Cain will be able to get off of his back.
Despite his size disadvantage, Cain isn't going to have a very big speed advantage in this fight. I just think he's giving up too much size and strength to match up with Brock, and honestly I see Brock pounding him out in the fight.
Let's hope I'm wrong.