Saturday, September 29, 2007

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.

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At Sunday, September 30, 2007 8:36:00 AM, Anonymous Guy said...

If anything, 20 runs probably overstates the case. The splits you use include PAs when the DBacks are winning by over 4 as well as losing, so fewer thatn 836 PAs are in losing blowouts. And because the DBacks lost most of their blowouts, their pitchers' OPS split probably isn't that unusual. Once you know that a team has lost most of their blowout games, you should expect to see that their pitchers performed poorly because it's likely the pitcher in question is a weak starter (i.e. not Webb) or a mop-up reliever). If you look at the 4 teams with the worst records this year (TB, BAL, KC, PIT), their pitchers have an average OPS of .806 in the 4+ run differential PAs, same as AZ.

What we really want to know is how DBacks pitchers performed in blowout losses, and then compare that to average performance in blowout losses. But even if DBacks were worse, you've shown the difference can't be enough to explain more that a couple of wins, if that.

At Sunday, September 30, 2007 9:12:00 AM, Blogger Phil Birnbaum said...

Right, that makes sense ... for bad teams, their "4+" score is mostly losses, while for good teams, it's mostly wins.

Since the DBacks did indeed have mostly losses, their "4+" score is as expected, and there's no evidence that it's due to the manager.

And as you say, even if the difference IS due to Melvin, it's a couple of games at most.

Did I rephrase your argument correctly? Thanks, it sounds reasonable to me.

At Sunday, September 30, 2007 1:10:00 PM, Anonymous Anonymous said...

Phil, why did you double the 10 runs for 3 and 4 run games when according to your numbers, the OPS against for 3 and 4 run games was .743, close to average?

Also, I just want to confirm that those B-R numbers are hitters' and pitchers' performance when the game is "already a blowout," (or whatever the run differential is) and not the entire game when the final score is a blowout?

At Sunday, September 30, 2007 8:57:00 PM, Blogger Phil Birnbaum said...

I doubled it just to give the Melvinites the benefit of the doubt. I figure, if Melvin is affecting the 4+ run games, maybe he's also affecting the 4-run games, and it's just not showing up in the stats.

But even if you double it, you don't get much of an effect.

I'm pretty sure the stats at baseball reference are for the score *at the time*. One reason is that those breakdowns are called "clutch". A better reason is that you can't have a tie game final score.

At Monday, October 01, 2007 7:05:00 AM, Anonymous Anonymous said...

"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"

I could of course be misreading Rosenheck's argument, but how can he assert that the Arizona clutch hitting has been excellent when the Diamondback OPS in every run-differential situation presented is lower than the league average? Yes, the Diamondbacks when close put up an OPS superior to that when they are not close. Compared to the analogous MLB OPS values, though, it is evident that the Arizona OPS is well below average in non-close situations, but just below average in close situations. Had Rosenheck asserted that Arizona hits better in the clutch than it does otherwise, I could accept such an argument; to assert that Arizona "clutch hitting has been excellent" is to ignore the unfavorable comparisons between the Arizona and MLB OPS.

At Monday, October 01, 2007 7:46:00 AM, Blogger Phil Birnbaum said...

The DBacks clutch hitting was excellent *relative to their non-clutch hitting*. When you're talking about Pythagoras, it doesn't matter that Arizona's clutch-situation hitting was below league average, just that it was above Arizona's average.

Even if you're the 1962 Mets, if your hitting is concentrated when it's most important, you're going to win more games than if you score the same number of runs when they're less important.

At Thursday, January 01, 2009 5:59:00 AM, Blogger sexy said...







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At Monday, May 25, 2009 2:43:00 AM, Blogger Kevin said...



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