When considering the nature of "uncertainty of outcome" as a (diminishing) component of the professional sport product, we are really considering three types of uncertainty: natural uncertainty, probablistic uncertainty, and aesthetic (or improvisational) uncertainty.
Natural uncertainty includes things like the weather or other "acts of god" such as injuries. These are certainly significant (imagine how snow would change the game plan for an NFL playoff game), but not what the consumer pays to see.
Probablistic uncertainty would consider whether a player actually makes the appropriate play in a given circumstance. Sabermetricians claim that there is no such thing as a clutch hitter, and that a hitter with good stats will end up having more "big" hits. I don't think this is what fans are paying for either; it would be akin to saying there is skill involved at the casino.
Aesthetic uncertainty is what I'm interested in. In most sporting situations, there is an appropriate defensive counter for any offensive move, and vice-versa. The discipline of an offence and defence allows athletes a degree of productivity, but what do most coaches fear of a star player? They fear his or her ability to break out of the predictability of Foucauldian discipline — they fear the improvisational, the aesthetic.
And so it is in broader society: we fear the unpredictable, the deviance from modern discipline, the uncertain.
That's what we pay to see at a sporting event, though.