Moneyball - Michael Lewis [66]
The beauty of the value of that hit (or catch) was that the game gave it to you; the game told you how valuable every event was, by telling you how valuable it had been, on average, over the past ten years. By listening to what the game told him about the value of events, Paul could take every ball hit between in the area broadly defined as center field and determine its “expected run value.”
Which brings us back to Johnny Damon. Over the 2001 season many hundreds of balls had been hit by opponents of the Oakland A’s in the vicinity typically covered by the center fielder. By totaling up the outcomes when Johnny Damon was in the field, and comparing them to the average, Paul was able to see how many runs Damon had saved the team. He was also able to estimate how many runs Damon’s likely replacement, Terrence Long, would cost the team. Some of this you could see with the naked eye, of course. You could see Johnny Damon break the instant the ball left the bat. You could see Terrence Long freeze, or even take off in the wrong direction, when the ball was in midflight. You didn’t really need Wall Street traders to tell you which one was the better center fielder. The system born on Wall Street simply helped Paul to put a price on the difference. There was no longer any need to guess. There was no need for gut instinct, or conventional fielding statistics. The total cost of having Terrence Long, rather than Johnny Damon, in center field was fifteen runs, or about a run every ten games.
Fifteen runs was not a trivial number. In the end, Paul concluded that Johnny Damon’s fielding was more important than Billy Beane believed—the first pamphlet Billy had read on the subject had said that fielding was “no more than 5%” of baseball—but not so much more that you wanted to pay Johnny Damon the $8 million a year his agent was asking for. And the truth was that you still couldn’t make perfectly definitive statements about fielding. “There was still no exact number,” Paul said, “because the system doesn’t measure where a defensive player started from. It doesn’t tell you how far a guy had to go to catch a ball.” What looked like superior defense might have been brilliant defensive positioning by the bench coach.
There was one other big glitch: these sorts of calculations could value only past performance. No matter how accurately you valued past performance, it was still an uncertain guide to future performance. Johnny Damon (or Terrence Long) might lose a step. Johnny Damon (or Terrence Long) might take to drink, or get divorced. Johnny Damon (or Terrence Long) might decide that he’d made enough money already and lose his middle-class enthusiasm for running down fly balls. In human behavior there was always uncertainty and risk. The goal of the Oakland front office was simply to minimize the risk. Their solution wasn’t perfect, it was just better than the hoary alternative, rendering decisions by gut feeling.
Of one thing they were certain: their system brought you a lot closer to the true value of a player’s performances than anything else like it. And it reinforced the Oakland A’s working theory that a guy’s hitting ability had a far greater effect than his fielding ability on a team’s performance. Albert Belle missed more fly balls than any other left fielder in baseball, but the system proved that he more than made up for it by swatting more doubles. Or as Paul put it, “The variance between the best and worst fielders on the outcome of a game is a lot smaller than the variance between the best hitters and the worst hitters.” The market as a whole failed to grasp this fact, and so placed higher prices than it should on defensive skills. Thus the practical answer to the question about Johnny Damon’s defense: it would probably cost more to replace than it was worth. Anyone who could play center field so well as Damon was either a lot worse offensively than Damon, or overpriced. The most efficient way to offset the loss of Johnny Damon’s defense was to