Tuesday, April 7, 2009
Computer simulations sometimes offer surprises
Alan Schwarz on the utility within baseball of computer simulations:
Take the age-old question of how much difference a team's lineup order makes. This issue so vexed the former manager Billy Martin that he once literally picked his Detroit Tigers batting order out of a hat.
Luke Kraemer of Imagine Sports, which owns Diamond Mind, programmed the simulator to force the 2008 Yankees to bat their best hitter and cleanup man, Alex Rodriguez, ninth -- to see how scoring was affected. Mr. Kraemer got the run total not for just one season, which can fluctuate as much as 80 runs in each direction from simple randomness, but for 100 seasons -- more than 16,000 Yankees games in all.
The result? The Yankees scored 747 runs per season, 40 fewer than their real-life 787. (Diamond Mind was so accurate that 100 seasons with A-Rod batting fourth averaged 789, almost dead-on.) Most research suggests that those 40 runs would mean only about four fewer victories, for a strategy no manager would ever consider; so the difference with Rodriguez batting third or fifth would be insignificant, and nowhere near worth the forests of trees that would give their lives to the ensuing sports-page debate.
The stolen base. Advancing from first to second puts the runner in scoring position, but he -- and the rest of your hitters -- will have a hard time scoring if he gets thrown out. Mr. Kraemer looked at a recent team that ran wild (the 2008 Tampa Bay Rays) and one that barely stole at all (the 2005 Oakland A's) and switched their mind-sets to see what happened. The A's scored 20 runs fewer, which probably says more about their players' inability to run in the first place. But when the speedy Rays stole sparingly, they increased their scoring by 47 runs per season -- suggesting that perhaps the Rays were running too often in real life.
The first of those is no real surprise; we know there's a real difference between lineups, but there's no real difference between reasonable lineups. You would score many fewer runs with A-Rod batting ninth (rather than fourth) because batting him ninth costs him roughly 90 plate appearances and a fair number of RBI opportunities. But the difference between batting him fourth and third or fourth and fifth is negligible, and worth worrying about only after you've figured out everything else.
On the other hand, the note about the Rays' steals is truly surprising. The generally accepted break-even point for steals is something between 70 and 75 percent (depending on the scoring environment). Well, last season the Rays stole 142 bases and were caught 50 times for a 74 percent success rate, comfortably within that break-even range. I don't know how to square 74 percent with those theoretical 47 runs
but if I were running the Rays, I sure would want to know.