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May 17, 2009

Prospectus Idol Entry

Brian Oakchunas' Initial Entry

by Brian Oakchunas

Bio: I love lounging around on summer days and watching baseball, but I also love to read great baseball work as well as do my own analysis and writing. In fact, I'd say I spend a solid 72% of my days thinking about baseball (don't ask about the other 28%). My obsession has resulted in ranking 39th lifetime in the National Fantasy Baseball Championship and what seems like a lifelong dream of writing for BP.

Entry: The Gibbons Conundrum: Effects of Defense on Pitching

Jeremy Guthrie, rookie pitcher for Baltimore, out of nowhere, had been taking the league by storm when he stepped onto the hill on July 12th, 2007 against the White Sox. He easily recorded the first couple outs before Jim Thome hit a drive to deep left. The ball barely cleared the wall and most defenders would have caught it, but Jay Gibbons couldn't haul it in and a homer as well as an extension of the inning was placed on Guthrie's line. The Sox kept hitting before a hit straight at Gibbons went through his legs, preventing him from throwing out the runner at the plate. The next batter to hit a can of corn, as Hawk Harrelson might say, was Rob Mackowiak, again dropping in an easy flyball near Gibbons that most fielders would have gotten to. When the inning was over, four runs had crossed the plate on Guthrie's watch, three of them earned but all of them were due to the negligence of Gibbons, prompting Guthrie fantasy owners everywhere to post messages on their league board, like, "Hey, Jay Gibbons, @%*# YOU!"

It is no secret among the initiated that errors are a poor way to judge whether defenders are effective. In recent years, more effective ways to judge defense have been developed-some such as John Dewan's Plus/Minus and Michael Lichtman's UZR use detailed play-by-play information. Major league clubs have also worked on their own interior evaluation systems because they realize that preventing runs via defense can be nearly as important as pitching and hitting. Dewan made this point in a recent Sports Illustrated article: "The difference between the best defensive team in baseball and the worst defensive team in baseball is about 130 runs. On the batting side, the difference between the best and the worst team is about 260 runs. To think that the value of fielding is worth as much as half the value of offense, I don't think anyone would have thought that. That's a significant number."

What Dewan doesn't note is that it is his number. His defensive system is well respected and certainly better than the archaic scorekeeper stats, but how do we know whether he's evaluating defense correctly? And it leaves us with questions about how many runs extra or less a specific pitcher is giving up due to his defense. We know defense is important, but exactly how important is an intriguing area for study.

The easiest and most accurate way to judge team defense has long been through defensive efficiency (DEF_EFF or DER)-a measure of how many balls put into play were converted into outs by a team's defense. Unfortunately, this metric doesn't help us evaluate individual players, but since pitchers have little control over the destiny of balls in play, it is a pretty good measure of team defense.

It also has quite an effect on both the RA and ERA of players and teams. In order to study the effect, I took each pitcher's performance in the MLB over the last 5 years and looked at the Deff_Eff, ERA, and RA of each one (weighted by the number of innings each pitcher threw). I then separated these pitchers into two groups, ones who had good defensive support (better than the .6924 average) and ones who happened to get the more inept (or hungover) group of fielders. Some profound results came up. The better group had a Deff_Eff of .718 with a 3.85 ERA and 4.16 RA. The less fortunate group had a Def_Eff of .666 with a 4.97 ERA and 5.41 RA. This works out to each .001 or thousandth of a point of Deff_Eff being worth .0215 runs of ERA and .024 runs of RA. That may not sound like much, but when you consider that the best and worst teams are often 40 thousandths of a point of Deff_Eff, it is quite a bit. You'll also note that the errors affecting ERA really don't make much difference.

What does all this mean? For one thing, it means that Tampa Bay team last year had a much better ERA than the year before because they had a great defense posting a .710 Deff_Eff, not because their pitchers (much the same as the year before) learned how to pitch. It also means that Texas pitching would be somewhat less horrid if their fielders got to balls a little more often than 67% of the time.

Let's take a look at how team ERA would have fared in 2008 if they had average pitchers, but were adjusted only by their Deff_Eff:

TEAM  DEF_EFF    ERA  Adjusted ERA
TBA     0.71    3.82   4.04
CHN     0.705   3.87   4.15
TOR     0.704   3.49   4.17
OAK     0.7     4.01   4.25
BOS     0.699   4.01   4.27
NYN     0.698   4.07   4.30
MIL     0.698   3.85   4.30
HOU     0.698   4.36   4.30
SDN     0.696   4.41   4.34
PHI     0.696   3.88   4.34
SLN     0.695   4.19   4.36
ATL     0.694   4.46   4.38
FLO     0.693   4.43   4.40
ANA     0.692   3.99   4.42
LAN     0.691   3.68   4.45
KCA     0.69    4.48   4.47
WAS     0.689   4.66   4.49
BAL     0.688   5.13   4.51
MIN     0.687   4.16   4.53
CHA     0.686   4.06   4.55
ARI     0.686   3.98   4.55
CLE     0.686   4.45   4.55
SFN     0.685   4.38   4.58
DET     0.685   4.9    4.58
NYA     0.682   4.28   4.64
SEA     0.682   4.73   4.64
COL     0.678   4.77   4.73
PIT     0.675   5.08   4.79
CIN     0.673   4.55   4.83
TEX     0.67    5.37   4.90

Clearly, the teams with better Deff_Eff had better ERA's but we can also see that their ERA's adjusted only by defense weren't far off from their actual effectiveness. The caveat here is that the ballparks have some effect, but most of what you see here is the defense in action. In terms of pitching, the same pitcher could end up with an ERA higher or lower by almost a whole run depending on the team for which he pitches. If you spent last year wondering why the Yankees or Tigers started with promising pitching staffs that finished poorly, you can see the holes in which their fielders were putting them.

Let's go back to Dewan's quote. He posited that the difference between the best and worst fielding teams is 130 runs. In the case of DER, it should have been .86 runs per 9 innings, or 138 runs over a full season (roughly 1,450 innings). This helps to support not only the validity of Dewan's work but also the whole idea that defense weighs heavily on pitching stats. Next time you like a pitcher for the upcoming season, do what I do and consider whether he has a team of Jay Gibbon's bad days behind him.

Related Content:  Defense,  Jay Gibbons

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