I really don't like Brock, but I think he will be able to take this fight to the ground and secure another victory.
Cain's a badass and he has heavy hands, but I really have a hard time seeing him defend Brock's takedowns. Gonzaga got Carwin down without a problem and secured a full mount. I can just imagine what Brock will be able to do...
Either Carwin will avoid the takedown long enough to keep it standing and catch Lesnar with a huge shot that will end the fight, or Brock will take Carwin down and work the ground & pound, score a TKO or a Unanimous Decision.
Brock seems very serious and extremely motivated too.