Monday, December 05, 2005

Run Prevention

The goal of every baseball team when they are not at bat is to give up as few runs as possible. This, of course, is done with pitching and fielding. The problem is how to separate pitching from fielding so we can evaluate each one of them in isolation. Because pitching and fielding are so intertwined this is not an easy task. However, sabermetric advancements are being made.

The first person known to quantify team fielding ability in a useful way was Bill James in his abstracts published in the 1980s. He developed a measure which he called Defensive Efficiency Ratio (DER). DER is the percentage of times batted balls are turned into outs by the team's fielders, not including homeruns. There are different versions of the formula but the one now most commonly used is DER=(BFP-H-K-BB-HBP-0.6*E)/(BFP-HR-K-BB-HBP) where BFP = batters faced pitcher, H=hits allowed, K=strikeouts, BB=walks allowed, HBP=hits batsmen and E=errors.

Pitching is more complicated. For years the only attempt to isolate pitching from fielding was ERA which was supposed to remove the effect of fielding errors from runs allowed. ERA is flawed, in part, because it is dependent on the whims of different official scorers. More importantly, it does not take into account the ability of fielders to get to balls.



In 2000, Voros McCracken published the results of his study which showed that there is little difference among major league pitchers in their ability to prevent hits on balls hit in the field of play. This conclusion was met with much skepticism even in the sabermetric community. His theory has been tested rigorously and weakened somewhat but his main concept has so far been shown to be true. That is, hits allowed by pitchers are more a function of team fielding ability than the ability of the pitcher.


The idea is that the contribution of pitching to overall team defense can be derived, for the most part, from walks allowed, strikeouts, homeruns allowed and hits batsmen issued. McCracken referred to those as Defense Independent Statistics (or DIPS). Tangotiger derived a statisctic from DIPS called Fielding Independent Pitching (FIP). FIP measures pitcher performance essentially independent from fielding. The formula is HR*13+(BB+HBP)*3-K*2)/IP plus a league specific factor to make it equivalent to ERA.


At the Major League Baseball Graphs site, it was reported that 82% of ERA variance by pitchers is explained by FIP and DER. This is a fairly high correlation and it supports the theory that FIP and DER tell you most of what you need about run prevention. Furthermore, they found that FIP, by itself, explains 54% of the variation in ERA and that DER, by itself, explains 31% of the variation in ERA. This tells us that pitching is more important to run prevention than fielding but that fielding is also essential. In short, what Bill James has always said is true: “Much of what we think of as pitching is actually fielding”.


So we have DER to measure overall team fielding and FIP to measure overall team pitching. This doesn’t explain everything about run prevention but it does a pretty good job. The table below shows the runs allowed (RA), ERA, FIP and DER for each American League team in 2005. These figures were abstracted from The Hardball Times Baseball Annual.


Team

RA

ERA

FIP

DER

CLE

642

3.61

3.94

.711

LAA

643

3.68

3.91

.700

CHA

645

3.61

4.14

.713

OAK

658

3.69

4.11

.717

MIN

662

3.71

4.03

.703

TOR

705

4.06

4.44

.701

SEA

751

4.49

4.59

.702

DET

787

4.51

4.60

.696

NYA

789

4.52

4.30

.691

BAL

800

4.57

4.54

.693

BOS

805

4.74

4.30

.683

TEX

858

4.96

4.40

.682

KC

935

5.50

4.76

.667

TB

936

5.39

4.92

.682

Avg.

758

4.35

4.35

.696


The following tables lists the ranks for each team in RA, ERA, FIP and DER


Team

RA Rank

ERA Rank

FIP Rank

DER Rank

CLE

1

1

2

3

LAA

2

3

1

7

CHA

3

2

5

2

OAK

4

4

4

1

MIN

5

5

3

4

TOR

6

6

9

6

SEA

7

7

11

5

DET

8

8

12

8

NYA

9

9

6

10

BAL

10

10

10

9

BOS

11

11

7

11

TEX

12

12

8

12

KC

13

14

13

14

TB

14

13

14

13


It can be seen in the first table that the Tigers gave up 4% more runs than the league average. Most of that was due to poor pitching (FIP was 6% above league average). Their fielding (DER=.696) was league average.


In the second table, it can be seen that the Tigers ranked 8th in run prevention. They had the 12th best pitching in the league but their fielding was ranked 8th. This is not to say that fielding is more important in run prevention than pitching. The ranks came out strange because there were a bunch of teams with similar RA. I think it does say that their average fielding helped out their poor pitching somewhat though.

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