I've always wondered what other people would think. If you take a Ninja, or a Samurai from the ancient dynasties, and brought him to the future, and put him in the octagon for hand to hand combat with a MMA champion, how do you think the match would go?
It wouldn't last very long, even if you took a modern practitioner or Ninjutsu. We don't train to fight with rules. If it were a fight with no rules then the Ninjutsu practitioner would probably win fairly quickly if they were decent at Ninjutsu.