I'm probably not alone in paying at least some attention to run differential when perusing the standings. It's a quick way to guess which teams have been better or worse than their record would indicate. Other than the existing seven games' difference, is there really much to separate the 35-24 Brewers from the 28-29 Rockies going forward if they have the same +26 differential?
Dave Cameron has published some expected run differential numbers at FanGraphs, which go a step further. Run differential tells us whether a team was particularly lucky with the timing of runs scored and allowed; xRDiff tells us whether some of the runs themselves were lucky. I like xRDiff a lot, and hope to see it installed at FanGraphs.
Even wOBA, though, incorporates a bit of luck in small samples, since whether a batted ball falls in for a hit isn't completely under a batter's (or pitcher's) control; we know line drives are hits about 70% of the time, for example. And with xBABIP not yet readily available, I thought some folks may want to see how Inside Edge numbers can shed some light on teams' run prevention to date.
I found a non-zero correlation between RA9-FIP and the percentage of batted balls that Inside Edge deemed unplayable (.386). That's a sign, in my eyes, that there is at least some luck to the 0% figures that has shown up in the standings -- especially since the rate of unplayable batted balls has no relationship with FIP (-.030). BABIP is still the answer, as it shows a very high correlation with RA9-FIP (.821). Still, I think these Inside Edge numbers have a role to play; BABIP tells us how and whether batted balls were actually handled, but the Inside Edge numbers help isolate the part of that that no fielder could have done anything about.
"0% TP%" is the percentage of batted balls deemed unplayable by Inside Edge for each team as it was pitching. I've also included "0-10% TP%," which is the percentage of batted balls that Inside Edge labeled as either being unplayable (0%) or very difficult (1-10%). So, I give you the teams that maybe kinda sorta had good or bad luck in terms of runs allowed (click to sort). Don't take it as gospel, but it might shed some light on hard luck clubs.
|Team||BABIP||RA9-FIP||0% TP%||0-10% TP%|
. . .
All statistics courtesy of FanGraphs.
Ryan P. Morrison is a featured writer at Beyond the Box Score, and co-author of Inside the 'Zona, a site on the Arizona Diamondbacks with a sabermetrics slant. You can follow him on Twitter: @InsidetheZona.