Its a tough fight to call: Cain has had another long layoff due to injury, so who knows if ring rust will play a factor. A few years ago, I would have said Cain would have probably won easily, due to Werdum's lack of a standup game (remember when he constantly fell to the ground and tried to pull Overeem into his guard

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Werdum appears to have significantly improved his striking game. He is currently on a five fight win streak coming off of the knockout win against Mark Hunt. He has always been one of the best BJJ practitioners in the world, and Cain could easily get subbed if he isn't careful.
Cain should keep the fight standing as long as possible, and only go for takedowns to get points, and only stay on the ground if he maintains a dominant position. All of the wrestling ability in the world will not prevent someone from tapping out

Should be an interesting fight.