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 (6^th in the AL) as he does on most fielding independent stats. Kenny Rogers (ranking 14^th with .538) and Nate Robertson (16^th with .536) are also in the top third in the league. Justin Verlander (27^th 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