Wednesday, December 27, 2006

Run Preventing Events

Today, I’ll continue with the batted balls versus pitchers theme which I started earlier this week. An at bat can result in any of the following events:


  • Strikeout
  • Base on balls
  • Hits batsman
  • Ground ball
  • Line drive
  • Outfield fly
  • Infield fly

Three of those events are generally favorable events for pitchers:


  • Strikeout
  • Ground ball
  • Infield fly

I will call these run preventing events (RPE). Of course, a ground ball is not as easy an out as a strikeout or an infield fly and can have a negative result for a pitcher. However, inducing a lot of ground balls will help to prevent runs over the course of a season. On the other hand, it is good for pitchers to avoid, for the most part, the following events:


  • Base on balls
  • Hits batsman
  • Line drive
  • Outfield fly

So, I thought it would be interesting to calculate the run preventing event percentage (RPE%) for American League pitchers in 2006 where RPE% = (SO + GB + IFF)/BFP. Striking out batters and inducing grounders have been shown to be repeatable skills. Getting batters to hit infield flies is not stable from year to year (correlation = .10 between 2005 and 2006). However, infield flies are relatively rare compared to other batted ball types and including them does not change the RPE% substantially in most cases. Plus, I suspect (without statistical evidence) that this is a real ability for some power pitchers.


It turns out that RPE% is fairly stable with a .66 correlation between 2005 and 2006. It can also be considered a fielding independent stat because, although the end result is not independent of fielders, getting a grounder or infield fly to happen in the first place has nothing to do with fielders. It is as stable or more stable than FIP ERA but it is not weighted and thus does not explain as much about runs allowed. RPE% is just an exploratory stat for now.


There were 48 American League starters with 125 or more innings pitched in 2006. Table 1 lists the RPE% rankings for Tigers starters. Table 2 lists the top 20 pitchers in the league. We can see that Jeremy Bonderman (RPE%=.585) ranks very well (6th in the AL) as he does on most fielding independent stats. Kenny Rogers (ranking 14th with .538) and Nate Robertson (16th with .536) are also in the top third in the league. Justin Verlander (27th with ,506) is in the middle of the pack and will likely need to improve his strike out and/or ground ball rate in 2007 if he is going to keep his ERA down.


Table 1: Run Preventing Events for Tigers Starters in 2006


Rank

Name

BFP

SO

GB

IF

RPE

RPE%

6

Bonderman

903

202

306

20

528

.585

14

Rogers

849

99

340

18

457

.538

16

Robertson

881

137

312

23

472

.536

27

Verlander

776

124

244

25

393

.506

---

Ledezma

264

39

67

15

121

.458

---

Maroth

234

24

81

4

109

.466

---

Miner

398

59

144

8

211

.530


Table 2: Top 20 AL Starters by RPE% in 2006


Rank

Name

Team

BFP

SO

GB

IF

RPE

RPE%

1

Halladay

TOR

876

132

404

22

558

.637

2

Hernandez

SEA

816

176

331

10

517

.634

3

Wang

NYA

900

76

484

7

567

.630

4

Westbrook

CLE

904

109

447

7

563

.623

5

Burnett

TOR

577

118

208

14

340

.589

6

Bonderman

DET

903

202

306

20

528

.585

7

Santana

MIN

923

245

255

32

532

.576

8

Sabathia

CLE

802

172

261

26

459

.572

9

Mussina

NYA

804

172

251

36

459

.571

10

Bedard

BAL

844

171

292

14

477

.565

11

Kazmir

TB

610

163

165

14

342

.561

12

Haren

OAK

930

176

316

29

521

.560

13

Schilling

BOS

834

183

247

28

458

.549

14

Rogers

DET

849

99

340

18

457

.538

15

Escobar

LAA

789

147

263

13

423

.536

16

Robertson

DET

881

137

312

23

472

.536

17

Contreras

CHA

833

134

283

29

446

.535

18

Johnson

NYA

860

172

258

30

460

.535

19

Millwood

TEX

907

157

309

18

484

.534

20

Beckett

BOS

868

158

282

23

463

.533

5 comments:

  1. This is awesome stuff Lee. I like the simplicity of the stat in that it's simply looking at a rate for good stuff versus bad stuff.

    I'm assuming that it correlates with runs allowed pretty well?

    ReplyDelete
  2. Bill, it has a moderate correlation with runs scored: -.50 for 83 AL pitchers with 162+ IP in 2005 or 2006. The correlations for QERA (.55) and FIP (.67) are higher. I think I need to weight the events in order to get a really high correlation. But then it loses its simplicity and becomes another FIP or QERA stat.

    It does seem to be reasonably predictive though. As I said in the post, it was stable from 2005 to 2006 for 40 AL pitchers with 17 or more starts both years. Also, RPEPCT in 2005 has a .47 correlation with run average in 2006 for 40 pitchers with 17 or more starts in both years. The correlations with 2006 run average for other 2005 stats are: ERA .39, FIP .50 and QERA .40. 40 data points is not enough though so I'll look at this again when I get more years of data.

    ReplyDelete
  3. I had the exact same thoughts about weighting it.

    I think the .50 is pretty significant in that it shows that a pitcher's ability to "pitch good" only accounts for half of what happens in terms of runs scoring.

    ReplyDelete
  4. Quick question -- where did the $126 million man rank? (I've been having fun with Bondo-Zito comparisons in recent days).

    ReplyDelete

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