BPIP and the Rays

by R.J. Anderson on May 25, 2008 10:36 AM EDT

A lot of people have talked about the idea of slugging percentage and the variety of hits being infused into WHIP, with a few vague references and 30 years worth (~4,300 samples) of 100 inning throwing pitchers BPIP was finally ready to make a return.

First let me explain what exactly it is: Bases Per Inning Pitched. Creative, I know, essentially it takes the total bases allowed, adds in the bases granted on walks, and divides them by innings. From there we can compare the correlation between BPIP and WHIP to confirm the suspected: BPIP has a much higher correlation to ERA (.7957) compared to WHIP (.63) and even FIP (.58) although do take into account that I used substantially less data for those two statistics. With the regression and equation, both listed on the chart below, we can plug the BPIP number in for a pitcher and get a projected ERA that, in theory, would be pretty close to the pitcher's actual ERA.

Bpip_medium

Now, let's actually use the projected ERA to see where the pitchers stand compared to their expected selves:

Bpipchart_medium

I'd like to focus initially on the rotation's results. Impressively each of our pitcher's has a pERA under 5. Scott Kazmir and James Shields have been really, really good. Edwin Jackson and Matt Garza have avoided the hit bug, despite some pesky walks, and Andrew Sonnanstine has allowed far too many extra base hits this year, but he's still a useful number five innings eater.

For the first time in franchise history the Rays actually have five pitchers who range from great to above average to average. Even if progression and regression don't even out perfectly the Rays have the makings of a rotation that can seemingly compete.

Along those same lines how good has J.P. Howell been in the bullpen? His velocity is the highest of his major league career (85.7 compared to 2005's 85.4) giving some water to the idea that the bullpen really will add velocity. Howell has been death against lefties (.452 OPS) and righties (.601) while doing exceptionally well in high leverage situations (.390 OPS in 23 at-bats). I don't know the Rays plans for replacing Al Reyes next year, but Howell might slide into the 7th inning slot allowing for dual cannon double inning action when combined with Dan Wheeler.

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Nice work

Very nice analysis RJ. Regarding Howell he has been excellent. I think next year Sonny will be doing exactly what Howell is doing this year. I am actually kind of interested to see Sonny’s splits between the first time he goes through an order, the second time, and the third time. Granted nearly all pitchers get worse as they go along, but my not so very care analysis thinks the splits are wider for him. So I think him and Howell would make a very deadly lefty/righty 1 to 2 inning specialists. The one guy I’m surprised to see with such a low pERA here is Wheeler. Maybe just a few of his bad innings stick in my mind but it seems like he has gotten into some major trouble and has given up some major hits.

by matthan on May 25, 2008 11:44 AM EDT reply actions

1st: .765, 2nd: .719, 3rd: .901for Sonny

"I've seen many, many blue skies turn gray, but the sun will eventually return, and so will I. So will I." - Carlos Pena

by R.J. Anderson on May 25, 2008 12:17 PM EDT up reply actions

Since it seems Wheeler is our designated stopper and always pitching in high-leverage situations, his slightest mistakes probably get magnified. Six runs in 22 appearances; a total of 17 scoreless appearances.. not bad.

Longlorious.

by RATW on May 25, 2008 3:56 PM EDT up reply actions

I can see that about Wheeler. I generally forget about his easy innings and just remember his games where he gives up a home run or ends up having to get out of a bases loaded jam.

by matthan on May 25, 2008 6:01 PM EDT reply actions

a question

Why is correlation to ERA a good thing? I mean, if we’re looking for a statistic that is really close to ERA, why not just use ERA? Or is it that BPIP has a high correlation to the following year’s ERA?

by MrIncognito on May 26, 2008 1:23 AM EDT reply actions

It gives us an idea of what ERA should be.

"I've seen many, many blue skies turn gray, but the sun will eventually return, and so will I. So will I." - Carlos Pena

by R.J. Anderson on May 26, 2008 1:26 AM EDT up reply actions

I don't follow

I don’t see how using bases per innings pitched helps minimize the contribution of team defense or several of the other confounding factors that limit ERA’s validity. While the correlation between the two may be high, that’s probably due to the fact that they measure essentially the same thing.

by MrIncognito on May 27, 2008 1:20 AM EDT up reply actions