Strikeouts and Ground Balls
The main tenet of defense independent pitching theory is that pitchers can only control strikeouts, walks and the types of batted balls (grounders, fly balls, line drives, pop ups) they give up. Under such a theory the best pitchers are those who give up few walks, line drives (likely to be hits), and fly balls (likely to be HRs), while getting lost of strikeouts, pop ups (almost always outs) and ground balls (rarely extra base hits). In this short post I want to consider the relationship between strikeouts and ground balls. The holy grail of pitchers is the one who can get tons of strikeouts and ground balls, while giving up few walks. Why is this combination so rare?
In black below is the relationship between whiffs (misses per swings) and the vertical location of a four-seam fastball. Also on the graph in blue is the relationship between ground ball per ball in play and vertical location. The graph is a little hard to understand because vertical location is the independent variable so it is along the horizontal axis, and there are two dependent variables displayed at the same time. The red lines indicate the average top and bottom of the strike zone.
The overwhelming trend within the strike zone is for whiff rate to increase with vertical location and for ground ball rate to decrease with vertical location. This is why it is rare to find an extreme ground ball pitcher who also gets a lot of strikeouts. The one exception here is the bottom of half foot of the strike zone where ground ball rate is very high and whiff rate has bottomed out and starts to rise again. If a pitcher could regularity locate in that bottom half foot, he could get whiffs and grounders, but as I noted last Friday it is important to consider just how accurately a pitcher can locate his pitches. Most likely few pitchers could regularity hit that spot.