Monday, March 22, 2010

The Oliver Perez Volatility Experiment

One of the things you hear as a Mets fan over and over again is how there is a "Good Ollie and Bad Ollie." That Oliver Perez is a coin flip. That you never know what he will give you on a given night.

It can be frustrating to watch the guy sometimes, but you may be surprised to learn that Oliver Perez is not much more or less "volatile" than any other average starter.

For the purposes of this discussion, volatility simply means the size of the gap between his good starts and his bad starts. A less volatile pitcher will have, obviously, less variation between the two. I am sure that many other, smarter people have tackled this issue, but I think seeing a graphical comparison between a few Mets will be helpful.

The below chart compares three pitchers. Oliver Perez and John Maine from 2007, the last season they both pitched full seasons, and Johan Santana from 2008. I included Johan as an exemplar of what an ace looks like in comparison to two average starters.

Each player has all their starts from the season arranged by Game Score in descending order[1].

Please forgive my very lame Excel and MS Paint skills.

Aside from the amateurishness of the graph, something should become immediately apparent to you: John Maine and Oliver Perez were very similar pitchers in 2007, and both were (obviously) worse than Santana.

The most interesting part, however, is this: John Maine had higher high scores than Perez, and lower low scores. It can hardly be argued that he wasn't more volatile than Perez that season, but you never hear him discussed in that fashion. Both pitchers clearly turned in some bad starts in 2007 along with their good ones - but any pitcher who struggles will do that.[2]

None of this is to say that Ollie isn't volatile. This isn't to say that he won't go out there and pitch terribly some days. What it IS to say, however, is that he's just like any other middle-of-the-rotation guy out there in the league. He's not going to be average every day.

We here at Fonzie Forever are going to make an ongoing effort to keep track of Oliver Perez and a few other pitchers to see whether the reputation he has earned is fair or not. To this writer, it doesn't seem to be. We'll keep track of his starts, some press clippings, and a few reference points, and track how he does this year.

Already this spring, I've noticed a few very funny disparities.
"John Maine started for the Mets this afternoon and he had a nice rebound effort, allowing just two runs and two hits in four innings..." Metsblog

"In an effort to keep his pitch count down, Perez said he focused more on throwing strikes and worried less about avoiding contact. The result? Eh. Not terrible. Not great. Perez gave up two runs on six hits in four innings against the Marlins" Star-Ledger

Stay tuned. As always, we appreciate your input, assistance, or any advice you have on the topic. Also, please follow us on twitter at @fonzieforever.

[1] Per wikipedia:

Game Score is a metric devised by Bill James to determine the strength of a pitcher in any particular baseball game. To determine a starting pitcher's game score:

1. Start with 50 points.
2. Add 1 point for each out recorded, so 3 points for every complete inning pitched.
3. Add 2 points for each inning completed after the 4th.
4. Add 1 point for each strikeout.
5. Subtract 2 points for each hit allowed.
6. Subtract 4 points for each earned run allowed.
7. Subtract 2 points for each unearned run allowed.
8. Subtract 1 point for each walk.

[2] It seems pretty clear that one of Santana's strengths in comparison to Perez and Maine was his ability to keep the Mets in games even on nights when he could not dominate.

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