Perhaps only the most fundamental of theists actually believe that it was Manny's prayers that got him to win fight after fight from one weight division to another. The moderate theists, on the other hand, probably believe that prayer has at least some bearing on his game, complimenting his hard work and preparation, so if he ever should come face to face with an equally skilled fighter, prayer would tip the balance to his favor.
If there was any branch of science that could have ever vindicated the doctrine of vitalism (the belief that something nonphysical is the force behind the phenomenon of life), it would have been molecular biology and its study of the genetic and chemical underpinnings of life.