Three months ago, the head coach of a professional football team made a terrible, terrible decision. On Sept. 30, up by a point with less than two minutes to go, Carolina's Ron Rivera decided to punt the ball away to the Atlanta Falcons, even though it was fourth-and-1, even though his team was on Atlanta's 45-yard line, even though he had Cam Newton. According to one post-game analysis, Rivera's punt cut his team's chances of winning by at least one-third. "This is it," wrote Aaron Schatz in Slate. "This play. Cam Newton is now our poster child for bad fourth-down decision-making."
Two days ago, a different head coach of a different professional football team made a different sort of decision. On Jan. 6, up by two touchdowns in the first quarter, Washington's Mike Shanahan decided to leave his rookie quarterback in the game, even though Robert Griffin III had tweaked his knee, even though Griffin had strained that knee the month before, even though Griffin had torn two ligaments in that knee in college. The Redskins lost, and Shanahan's quarterback may have two new partial tears in his knee ligaments. “Whatever reputation Shanahan had is forever scarred by this," wrote Dave Kindred on Twitter. "FIRE SHANAHAN. NOW."
But these scenarios are not the same. In one, we can say exactly why the coach was wrong. We can run the numbers to produce an estimate—not a perfect one, but a pretty good one—of Rivera's wrong-headedness. We can express his failure as a change in betting odds. In the other, there is no way to know if Shanahan was wrong or right. We can wring our hands and call him names, but we have no math to fortify our hindsight. We have only the crude and shaky logic of what happened.