Too many red flags on Smith side in my opinion.
That sweet UFC desk gig is not making fighters better. He was acting really strange in his last fight. He looked like shit in his last 2 fights. Personally I don't think he wants to fight any more, he is just collecting paychecks and he will occasionally do the UFC a solid stepping in on short notice to keep his desk job. I think he has mentally checked out from the fight game.
Spann isn't that good, but I think he is much more motivated at this point and that should be enough to win this one.