OPI: The Oliver Perez Index

Its time to break some new ground here on ihatethemets.net.  Inspired by Bill James’ Game Score and Oliver Perez’ 2009 season, I set out to develop a new statistic (because their aren’t enough already). The goal was to develop an index to describe how frustrating a pitcher is to watch, hence the choice of the “Oliver Perez Index” as the name of this stat.

Like the game score, I wanted to add up a few different pitching statistics such that perfection (or in this case, imperfection) gives a number around 100.  Unlike the game score, I wanted to use statistics accumulated by a pitcher over the course of a season. And unlike the Game Score, a higher score is bad.  But I didn’t want to just measure bad pitching, I wanted to measure annoying pitching, which involves the stats you’ll see below, such as % of opposing pitchers walked. I also wanted to avoid standard stats like walks or hits or home runs, because that would be boring.

After much testing (about half-an-hour after I got home from work tonight), I’m ready to reveal the Oliver Perez Index (OPI).  Here are the different stats that you add up to get the OPI, with the reasoning behind the inclusion of each stat:

• 9 – (Average IP per Game Start): A pitcher who doesn’t go deep into games is annoying
• Pitches thrown per inning – 12: After 12 pitches, any inning becomes increasingly more frustrating to watch
• % of plate appearances with a 3-0 count: Very frustrating, just throw a damn strike
• % 0-2 counts that end up with a walk: This was an Aaron Heilman staple
• % of leadoff batters walked: An Oliver Perez staple.
• % of opposing pitchers walked: Always unacceptable.
• 62% – % of strikes thrown: 62% of pitches in major league baseball are strikes. Any worse than that and you’re making your fans pretty frustrating.
• 49- Average Game Score: 49 is the average game score posted by starters over the last several seasons. Anything worse than that is increasingly frustrating to watch.
• Standard Deviation of Game Scores: A measure of how inconsistent a pitcher is across starts.

And here is Oliver Perez’ 2009 season:

9-AVG IP	4.7
(Pitches/Inning) - 12	8.8
% of 3-0 counts	8
% of 0-2 counts with a walk	12
% Leadoff Batters walked	25
% Opposing Pitchers walked	10
62 – Strike %	5
49 – AVG Game Score	16
STD Dev Game Scores	18.4
Total = Oliver Perez Index	107.9

 

I considered taking out the Pitches/Inning – 12 or % 3-0 counts to make Perez’ 2009 season = 100, which would have been pretty cool.  But I don’t mind if Perez’ brief 2009 performance surpasses 100. The highest game score on record is 105 (Kerry Wood, 2003), so I can see how these stats should be allowed to surpass 100 in extreme cases. 

What next? Well, in the coming days, I’ll try to use the OPI to evaluate some other Mets pitchers past and present and set out in search of any pitcher who can beat Perez’ 107.9 over a full season.

Also note that this stat only applies to starters.  If I like where the OPI is headed, I may have to start work on an Aaron Heilman index.

Addendum: Here’s an excel file you can use to calculate your own OPI. And here’s an interactive web version of that excel file (needs Internet Explorer to run)