The knuckleball is a difficult pitch to hit because of its unpredictable movement. But few analyses have ever looked at another component of the knuckleball: its speed.
According to the man himself, R.A. Dickey varies the speed on his knuckleball according to the situation. But how much, and in what way? Is this a common feature of knuckleballers, or relatively unique to Dickey?
In the PITCHf/x era, we really have only two knuckleballers with sufficient data to analyze, R.A. Dickey and Tim Wakefield (there are others, such as Charlies Haeger and Zink, but those pitchers have appeared only a very small number of times).
To answer this question, I pooled knuckleballs by count (1-2, 3-0, etc.) and looked at the standard deviation of the pitch mph within those counts. To visualize this data, I have plotted count, not as two separate categorical variables, but as count linear weights—the run value of being in a particular count (such as 0-2). This makes “count” one continuous axis ...