Platoon Splits for Three Types of Fastballs
On Friday I looked at the run value of four-seam, two-seam and cutter fastballs based on pitch movement. In that post I noted, that it looked like two-seam fastballs had very extreme and cutters almost no platoon split. This comment was offhand, and I did not demonstrate that was the case. In this short post I will do that.
A month ago I looked at the platoon splits of fastballs, changeups, sliders and curves. My results reconfirmed what John Walsh showed in the 2008 Hardball Times Annual: fastballs have an intermediate platoon split, sliders a very extreme one, and changeups and curves none. In that post I grouped all fastballs together. Based on those results and the results of last week's post I was very curious to see the platoon splits for the different fastball types.
These results are consisitent with the remarks I made on Friday:
- Two-seam fastballs have an extremely large platoon split, as big as the slider platoon split.
- The platoon split for cutters is not statistically significant.
- Four-seam fastballs have a small yet significant split.
Interestingly, there is no trend for pitchers to throw the pitches in different proportions to lefties and righties. Approximately 48% of all pitches are four-seam fastballs, 8% are two-seam fastballs and 4% are cutters with almost no difference in same- and opposite-handed at-bats for either RHPs or LHPs. This is very strange it would seem pitchers would do well to throw two-seams fastballs much more in same-handed at-bats, as they do with sliders, and cutters in opposite-handed at-bats, as they do with changeups.
One pitcher who does this, and I would guess this is a big reason for his success, is Jon Lester. Lester, a lefty, throws all three of these fastballs. Here are the proportion of pitches to RHBs and LHBs that are each of the three fastball types.
| Fastabll Type | RHB | LHB |
| Four-Seam | 0.317 | 0.322 |
| Two-Seam | 0.155 | 0.290 |
| Cutter | 0.133 | 0.077 |
This is the type of breakdown I think pitchers should use, way more cutters to opposite-handed batters and more sinkers/two seamers to same-handed batters. I am surprised that is the not the case generally. It would be interesting to see if successful pitchers, like Lester, are more likely to show this breakdown than the average pitcher.