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As most of you here know, walk, strikeout, and flyball rates are the most stable statistics for a pitcher from year to year. They don't tell you everything about a pitcher, but pitchers with similar peripherals are generally considered to be of the same skill. There are quite a few pairs of starting pitchers who had nearly identical peripherals during the 2012 season, some very similar and some not at all.
Methodology
The pitchers used for the study were the 88 that qualified for the ERA title with at least 162 IP. For the control stat, I used (BB - IBB + HBP)/(TBF - IBB). For strikeouts, I used K/(TBF-IBB), and I used raw FB%. From there, I converted each stat into a z-score, due to different variances in the stats. I then created a similarity score, summing the absolute values of the difference of each stat. There are no league or park adjustments, but these rates should be affected less than batted ball stats in that regard.
Results
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Justin Verlander | 6.6% | 25.1% | 35.6% | 0.50 | 1.41 | -0.35 | 0.00 |
| R.A. Dickey | 6.6% | 24.9% | 34.1% | 0.50 | 1.37 | -0.10 | 0.30 |
Stuff-wise, these two couldn't be any different. However, the two had near-identical walk and K rates, with Verlander allowing just a few more flyballs. So different, yet so similar...
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Felix Hernandez | 7.2% | 23.7% | 28.6% | 0.18 | 1.09 | 0.82 | 0.00 |
| James Shields | 7.1% | 23.7% | 29.0% | 0.24 | 1.07 | 0.75 | 0.15 |
Here is a pair that had similar environments last season, pitcher's parks in the AL. Despite his velocity being down, Felix still has power stuff, while Shields has an average fastball with a changeup as his go-to pitch. They even had similar mixes in BB and HBP, each hitting at least 10 guys.
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Kyle Lohse | 4.8% | 16.6% | 35.6% | 1.42 | -0.71 | -0.35 | 0.00 |
| Tom Milone | 4.8% | 17.4% | 37.3% | 1.39 | -0.51 | -0.63 | 0.51 |
This is the reason why teams aren't lining up to pay eight figures a year for Lohse. Take into account that Lohse got to face the pitcher most of his starts last year and still couldn't match Milone's K rate shows the disparity between Lohse's perception and reality.
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Mark Buehrle | 5.0% | 15.2% | 36.3% | 1.32 | -1.06 | -0.47 | 0.00 |
| Joe Saunders | 5.2% | 15.1% | 35.6% | 1.18 | -1.08 | -0.35 | 0.28 |
Not much to say here. Similar stuff, similar results.
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Jeremy Hellickson | 8.1% | 16.8% | 37.2% | -0.27 | -0.65 | -0.62 | 0.00 |
| Ervin Santana | 8.9% | 17.5% | 37.3% | -0.66 | -0.49 | -0.63 | 0.58 |
We are now on two completely different ends of the results spectrum. Hellickson is the new anti-DIPS posterboy, while Santana fell off the map. Being so close in sustainable skills, one would expect their results to converge this season.
| Name | BB% | K% | FB% | BBz | Kz | FBz | Sim |
| Jered Weaver | 6.6% | 19.2% | 42.8% | 0.48 | -0.05 | -1.55 | 0.00 |
| Wei-Yin Chen | 7.6% | 18.8% | 42.1% | 0.01 | -0.14 | -1.43 | 0.69 |
While Chen had a nice debut season in the U.S., he would not seem to be a likely candidate as the pitcher most similar to Weaver. Thriving on a constant low BABIP allowed, the Angels' ace has been living dangerously, which could come back to bite him soon.
It's interesting to see some of the different reputations rating very similar. This is definitely not an exact measurement of likeness, but it's fun to see what kind of comparisons you can draw from the core stats.