Why are the Diamondbacks outperforming Pythagoras?
As of yesterday, the Arizona Diamondbacks were 89-70. However, they have scored 11 fewer runs than they've allowed. According to the Pythagorean Projection, they should be 78-81. That's a difference of 11 games.
Normally, deviations from Pythagoras are just luck. The standard logic says that a team that "should" go 78-81, but goes 89-70 anyway, is probably really a 78-81 team that got lucky. You shouldn't expect that luck to continue.
But in a "Keeping Score" article in last Sunday's New York Times, columnist Dan Rosenheck argues that, in this case, Pythagoras is at least somewhat wrong:
" ... the Diamondbacks are clearly not as good as their record, but they’re not as bad as Pythagoras would have you think."
Rosenheck describes two reasons for the D-Backs' outperformance. First, their clutch hitting has been excellent. Here, courtesy of Baseball Reference, is their OPS when the score is tied, followed by when the score is one run difference, then 2, 3, 4, and more than 4:
.748 / .759 / .745 / .742 / .736 / .729
They hit much better when the game is close than when it's a blowout. The MLB averages show no such pattern:
.762 / .760 / .761 / .759 / .760 / .754
The Diamondbacks have hit well in the clutch. And (as Rosenheck acknowledges), since clutch performance is almost certainly not an innate ability, the "clutch" part of Arizona's discrepancy is probably random chance.
However, the flip side of clutch hitting is clutch pitching. On this, Rosenheck argues, manager Bob Melvin has expertly figured out how to reserve his best pitchers when the game is on the line, saving his worst pitchers for blowouts when the runs they give up don't matter much. "Of course," he says, "all teams pursue this strategy, but Melvin has done so more effectively."
This I'm not sure about. Here is Arizona's "clutch" line for pitching:
.726 / .735 / .738 / .743 / .743 / .807
Again, they're clutch, clutchier than average -- their pitchers are much better when the game is close, which again contributes to making them more successful than their Pythagorean projection.
But should this really be attributed to Bob Melvin? If he were doing something different from other managers – say, using a mediocre pitcher in a 3-run save situation, but maximizing Jose Valverde's leverage by using him in an eighth inning tie game – I might buy it. But the game log (for Valverde, at least) doesn't show anything unusual.
One thing that does stick out is the .807 at the end of the pitching line. Indeed, Arizona's pitchers are particularly mediocre once the game is out of hand. That might be a real effect, rather than luck: Melvin might be using really crappy pitchers, or just telling them to go easy on their arms in blowout games.
But even so, that category is only 836 plate appearances. If I've done the math right, the difference between .743 and .807, in that number of PA, is only in the range of 10 runs. Let's say we double that, assuming that Melvin's strategy has an equal influence in 3- or 4-run games. That's still only 20 runs, or two games.
My best guess is that it's all luck, except for a couple of games. I'd bet that the D-Backs are, in talent, around a .500 team.
Rosenheck and Chris Jaffe don't agree. I might be wrong; maybe there's something I haven't considered.