Wednesday, January 28, 2009

Tweaking RBI Percentage

Like it or not, RBI is still one of the most popular stats among mainstream baseball media and fans. It's not a terrible statistic. Most players with a lot of RBI are good hitters. However, the number of RBI a player aggregates is dependent on the number of opportunities his team gives him. Most hitters in the middle of the Rangers line-up last year had more opportunities to drive in runs than Athletics batters. A clean-up hitter will generally have more chances than a leadoff hitter. It's a very situation dependent statistic.

If it is power hitting you are trying to measure than slugging percentage or isolated power are more independent measures. If you are trying to measure a batter's success in getting runners home, one simple way is RBI percentage. There are a few ways to do this. The first one was created by David Pinto (Baseball Musings). RBI% is the percentage of runners on base that a player drives home in his plate appearances. It is calculated as follows: (RBI-HR)/runners on)*100.


The league average RBI% in 2008 was 14.5%. The Tigers are listed in Table 1 below and it can be seen that Miguel Cabrera was the Tigers best RBI man. Miguel Cabrera had 477 runners on base in his plate appearances last year. He knocked in 127 of those runners. Subtracting his 37 homers, that comes out to 90/477 = 18.9%. That Cabrera is number one is not a surprise. Magglio Ordonez at number two (17.7%) is also not unexpected. What might shock some of you is that Brandon Inge was third at 16.1%.


Table 1 - Tigers RBI% Percentages in 2008 (All plate appearances)

Player

Runners

HR

RBI

RBI%

Cabrera

477

37

127

18.9

Ordonez

464

21

103

17.7

Inge

249

11

51

16.1

Thames

205

25

56

15.1

Granderson

294

22

66

15.0

Guillen

323

10

54

13.6

Polanco

374

8

58

13.4

Renteria

339

10

55

13.3

Laird

269

6

41

13.0

Rodriguez

210

5

32

12.9

Sheffield

333

19

57

11.4



The RBI percentage in Table 2 is a little different from what Pinto does. Pinto includes all plate appearances in his RBI opportunities. Let's do the same calculation but try removing plate appearances when a batter walks or is hit by the pitch or gets a sacrifice bunt. After all, it is difficult for a batter to knock in a run if he being pitched around or thrown at or is asked to bunt. One could make the case that some batters draw too many walks in spots where they should be trying to drive home runs but it's also true that some batters get pitched around more than others.

The league average for this new RBI% statistic was 16.0%. Cabrera (20.3), Ordonez (19.5) and Inge (18.3) once again lead the list.

Table 2 - Tigers RBI% Percentages in 2008 (PA with BB, HBP, SAC excluded)

Player

Runners

HR

RBI

RBI%

Cabrera

439

37

126

20.3

Ordonez

415

21

102

19.5

Inge

213

11

50

18.3

Granderson

256

22

65

16.8

Thames

194

25

56

16.0

Guillen

278

10

53

15.5

Laird

242

6

41

14.5

Renteria

317

10

55

14.2

Polanco

346

8

57

14.2

Rodriguez

189

5

30

13.2

Sheffield

276

19

53

12.3


Finally, we'll try one more thing. What happens if we just look at situations where runners are in scoring position? The average American Leaguer knocked in 28.9% of runners in scoring position. Cabrera (35.0) and Ordonez (32.7%) lead the list again. This time Granderson is third at 32.2 but Inge is still above average at 32.0.

Table 3 - Tigers RBI% Percentages in 2008 (RISP only, BB, HBP, SAC excluded)

Player

RISP

HR

RBI

RBI%

Cabrera

220

8

85

35.0

Ordonez

208

2

70

32.7

Granderson

115

3

40

32.2

Inge

103

1

34

32.0

Guillen

139

1

39

27.3

Renteria

154

2

42

26.0

Polanco

167

2

45

25.7

Laird

130

3

36

25.4

Sheffield

128

5

37

25.0

Rodriguez

99

1

24

23.2

Thames

96

5

27

22.9


Yes, there are more accurate ways to measure how well batters produced runs in different situations. There is Win Probability Added for example. However, sometimes it's good to step back and do something a little more simple. I think RBI% is something that goes a little beyond RBI, yet is a little easier for some to grasp than some of the more advanced statistics.

The information used here was obtained free of charge from and is copyrighted by
Retrosheet. Interested parties may contact Retrosheet at 20 Sunset Rd., Newark, DE
19711.

1 comment:

  1. Jeff MorfordJanuary 30, 2009

    Inge is a clutch hitter.

    One could have fun with RBI% on message boards!

    ReplyDelete

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