Saturday, December 22, 2007

Run Preventing Events - 2007

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 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
Last year, I created a statistic I call Run Preventing Event percentage (RPE%) which is calculated as follows: (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 20065). 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. Part of the value of RPE% is its simplicity.

There were 65 American League starters with 17 or more starts in 2007. Table 1 lists the RPE% rankings for Tigers starters. Table 2 lists the top 20 pitchers in the league. In general, the RPE% seems to be good for identifying effective pitchers but it gives rather unusual results for a couple of Tiger starters: Jeremy Bonderman and Justin Verlander.

From the tables, we can see that Bonderman (RPE%=57.2) ranked very well (9th in the AL) and was the only Tigers pitcher in the top 20 in 2007. I mentioned in the starting pitcher FIP ERA article, Bonderman does well on fielding independent stats (strike outs, walks, ground balls) but allows runs in bunches, particularly in the first inning. His problems with runners on base are illustrated by his OPS against splits: .827 with runners on base, .888 with runners in scoring position and .748 with the bases empty.

In contrast to Bonderman, Verlander had an RPE% (52.1) which was close to league average. Verlander had a lower than average ground ball percentage (41%) but had very good results on fly balls and line drives. According to The Hardball Times Baseball Annual 2008, he allowed fewer runs per line drive(.32) than any American League pitcher. He also finished in the top 5 in runs per outfield fly (.14). This may be an indication that he did not allow well hit balls when runners were on base.

The other three pitchers expected to start for the Tigers in 2008, had RPE percentages of league average or just below: Kenny Rogers 52.0, Dontrelle Willis (51.5), and Nate Robertson (51.1).

The raw data used in calculating RPE% were abstracted from The Hardball Times database.


Table 1: Run Preventing Events for Tigers Starters in 2007

Rank

Name

IP

SO

GB

IF

RPE

RPE%

9

Bonderman

174.3

145

266

20

431

57.2

31

Verlander

201.7

183

245

23

451

52.1

34

Willis

205.3

146

322

17

485

51.5

41

Robertson

177.7

119

266

14

399

51.1

50

Durbin

127.7

66

193

17

276

49.2

.

Jurrjens

30.7

13

37

6

56

45.9

.

Maroth

78.3

28

120

9

157

45.4

.

Miller

64.0

56

102

7

165

53.4

.

Rogers

63.0

36

102

5

143

52.0



Table 2: Top 20 AL Starters by RPE% in 2007

Rank

Name

Team

IP

SO

GB

IF

RPE

RPE%

1

Hernandez

SEA

190.3

165

357

11

533

66.0

2

Carmona

CLE

215.0

137

431

8

576

65.5

3

Burnett

TOR

165.7

176

239

15

430

62.2

4

Bedard

BAL

182.0

221

216

12

449

61.3

5

Beckett

BOS

200.7

194

276

29

499

60.7

6

Wang

NYA

199.3

104

381

12

497

60.4

7

McGowan

TOR

169.7

144

264

10

418

59.3

8

Halladay

TOR

225.3

139

391

19

549

59.2

9

Bonderman

DET

174.3

145

266

20

431

57.2

10

Sabathia

CLE

241.0

209

324

25

558

57.2

11

Loe

TEX

136.0

78

269

3

350

56.9

12

DiNardo

OAK

131.3

59

249

7

315

56.8

13

Kazmir

TB

206.7

239

238

23

500

56.4

14

Westbrook

CLE

152.0

93

264

7

364

56.2

15

Haren

OAK

222.7

192

304

28

524

56.0

16

Shields

TB

215.0

184

279

25

488

55.8

17

Tavarez

BOS

134.7

77

252

8

337

55.8

18

Meche

KC

216.0

156

321

26

503

55.5

19

Gaudin

OAK

199.3

154

318

18

490

55.3

20

Blanton

OAK

230.0

140

359

26

525

55.3

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