Stability Check: Starting Pitcher Edition | The Process Report

Stability Check: Starting Pitcher Edition

Pizza Cutter published a classic article that finds when certain statistics stabilize. These numbers are a good benchmark to finding when we have a large enough sample size to start comparing data. Let’s look at each of these statistics for the Rays as they stabilize.

For pitchers, strikeout, groundball and line drive rate stabilize at 150 batters faced (BF). Fly ball rate and groundball/fly bal ratio stabilize at 200 BF. Since the top four starters have already passed both of these thresholds, we’ll look at all of them together.

Pitcher BF 2011 K/PA Career K/PA Difference
James Shields 294 0.25 0.20 0.05
David Price 280 0.20 0.20 0.00
Wade Davis 247 0.11 0.16 -0.05
Jeremy Hellickson 214 0.17 0.19 -0.02
Pitcher BF 2011 GB/PA Career GB/PA Difference
James Shields 294 0.31 0.32 -0.01
David Price 280 0.31 0.30 0.01
Wade Davis 247 0.26 0.28 -0.02
Jeremy Hellickson 214 0.27 0.27 0.00
Pitcher BF 2011 LD/PA Career LD/PA Difference
James Shields 294 0.14 0.14 0.00
David Price 280 0.16 0.13 0.03
Wade Davis 247 0.14 0.13 0.01
Jeremy Hellickson 214 0.14 0.12 0.02
Pitcher BF 2011 FB/PA Career FB/PA Difference
James Shields 294 0.23 0.27 -0.04
David Price 280 0.27 0.27 0.00
Wade Davis 247 0.37 0.32 0.05
Jeremy Hellickson 214 0.31 0.33 -0.02
Pitcher BF 2011 GB/FB Career GB/FB Difference
James Shields 294 1.32 1.16 0.16
David Price 280 1.16 1.1 0.06
Wade Davis 247 0.69 0.87 -0.18
Jeremy Hellickson 214 0.88 0.82 0.06

James Shields is striking out more batters this year and Wade Davis is striking out fewer. There aren’t any big differences in groundball or line drive rate. Shields is inducing fewer flyballs and Davis is inducing more. This is odd, since usually a pitcher who induces more flyballs will get more strikeouts, by virtue of pitching up in the zone.

The greatest difference for each pitcher is in groundball/flyball ratio. Shields, David Price and Jeremy Hellickson have all increased this ratio. Wade Davis is the lone pitcher who has decreased it.

From this, it is easy to see why Shields has been getting great results and Davis has not been. Shields has been striking out more batters while getting more groundballs. Davis has been striking out fewer batters and has been inducing more flyballs.



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