Minor League Walk Rates and Starting Pitchers

When I’m looking at pitching prospects, I always find myself defaulting to strikeout rates and “stuff” when I’m evaluating them. After all, in the majors, I see plenty of pitchers who have what I would consider a high walk rate and still have plenty of success. Then I thought of Adam Dunn, who struck out almost 27% of the time in the majors and still had success, but who was an entirely different player in the minors. Indeed, Dunn struck out just 18.2% of the time in the minors, and if he has seen so much change as he’s reached the majors, maybe some of the high walk major leaguer pitchers have, too.

I decided to take a look at any active, qualified pitcher with an adjusted ERA+ at or over 100 (or at or over league average). While accounting for league and ballpark, adjusted ERA+ isn’t perfect because it doesn’t account for fielding, but it’s more than sufficient for measuring performance, particularly over multiple years. At the time I pulled the data, the sample included fifty pitchers, from Roy Halladay to Dontrelle Willis. With the exception of Mariano Rivera, almost all pitchers spent at least some time as a starter, which makes sense considering qualification, but also is helpful for the purposes of the study since a large part of evaluating pitching prospects involves finding pitchers who will enter the big leagues and stick in a major league rotation.

The results were nearly staggering. The average minor league walk rate per nine innings for all pitchers on this list was just 3.172 (the median walk rate was just three walks per nine innings). Only 10 pitchers on the list had a walk rate at or over 4.0, and a number of them have elite, plus-plus stuff (Kerry Wood at 6.2 BB/9, C.C. Sabathia at 4.3 BB/9) while others really changed their careers with the development of new pitches (Tim Hudson at 4 BB/9, Cliff Lee at 4.2 BB/9). In other words, unless you have life-changing stuff or are in the minors for long enough to develop a new pitch, it’s extremely unlikely that a pitcher with an above average walk rate is going to make it as an above-average starting pitcher in the majors.

The sample is still relatively small, obviously, and there are plenty of holes to poke in it, but the way I look at it as follows: stuff and strikeouts can both make the difference between a league average starter and an elite starter with a similar walk rate; walk rate can effectively rule out a number of minor league pitchers from large-scale major league success as a starter. Since we looked only at those pitchers that met the innings limit for the statistic, we’ve effectively weeded out the pitchers that had some short-term success but who did not sustain it as a starter over the long haul. It also doesn’t show us relief pitchers who may have had high walk rates in the minors who had success in the majors, in large part because that’s exactly what you’re trying to avoid when prospecting. In other words, the goal is to find the pitchers who won’t have to move to the bullpen because a lack of stuff, a lack of command or a lack of repertoire.

The other reason this study was interesting to me was ultimately for fantasy purposes; everyone’s trying to find the next sleeper or the next undervalued pitcher who will yield long-term success for minimal money. In my case, I was looking particularly at Keyvius Sampson, J.C. Sulbaran and Jeurys Familia, all of whom are well-regarded for their stuff but all of whom have career minor league walk rates at or over four walks per nine innings. It tells me that if you’re going to gamble, you may want to gamble on the pitcher who can throw strikes and may get a bump in velocity through a tweak in mechanics or through physical projection as opposed to someone who cannot throw strikes but has the stuff to be successful otherwise.

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For those of you who are curious here are the minor league walk rates of the 50 pitchers I examined: