Pitch sequencing seems to be the next real frontier in Pitch F/X data studies, as evidenced by some good recent articles on the subject, including this one by Jon Roegele looking at strikeouts. In this post, I will look at home run sequencing, specifically, at-bats where there was a whiff, only to be followed by a homer later in the at-bat.
By my count, there have been about 420 at-bats this year in the Majors that ended in home runs but had a whiff (swinging strike) earlier in the at-bat. A whiff is the best possible one pitch outcome for a pitcher, and the home run is the worst outcome for a pitcher. The former shows that they can miss bats, while the later is an automatic run(s). I wanted to look at why some at-bats included both, and what that meant for pitch selection. We have all seen at-bats where the pitcher fools a hitter, only to give up a hit later in the at-bat. Then, with 20/20 hindsight, we usually complain that the pitcher either went to a different pitch than the one he initially fooled the hitter with, or that he thought he could do it twice, and MLB hitters adjust, and hit the homer the second time they see it. I wanted to see if there was evidence that the pitcher should continue to go to the same pitch they fooled the hitter initially with, or whether or not the homer usually came on the same pitch type (using MLBAM tags for this post).
Instead of doing it from a pitcher's perspective, I thought it might be helpful to look at it from a hitter's perspective, to see how they are adjusting (or whether or not they just hit the other pitch thrown). So the following sheet is the 420 at-bats, labelled by hitter with the whiff (or whiffs if there were two whiffs) pitch type and then the home run pitch type.
From my count, the hitter hit a homer on the same pitch he whiffed at 207 times, meaning the split was about 50/50 as to whether the pitcher was burned by going to a different pitch than he got the whiff on, or staying with the same pitch. This is with considering each and every pitch type as well. A pitcher may get a whiff with a cutter and then give up the homer with a moving fastball, and technically it is a different pitch, but it is still in the same family of pitches, that is, fastballs. For instance, there were 111 at-bats that turned into homers where the first whiff came on a 4-seam fastball. 75 of the homers turned out to be on 4-seam fastballs, and the number jumps up to 91 if you include cutters, 2-seamers, and sinkers. So it would seem that if a pitcher gets a whiff early in the count with a 4-seam fastball, they are far less likely to give up a homer later in that at-bat if they throw a breaking ball than if they throw a fastball. On the other hand, there were 88 at-bats that had a changeup whiff as the first whiff that turned into homers. 28 of them turned out to home runs off another changeup, and Just 21 of them turned out to be homers off of a 4-seam fastball. Just 4 of the at-bats that had a fastball whiff had changeups turned into homers.
So it seems, if a pitcher goes changeup/fastball or fastball/changeup (assuming they get a whiff on one), they are much less likely to give up a homer than if they throw changeup/changeup or worse, fastball/fastball.
16 of the 25 at-bats that had a sinker whiff as whiff one followed by a home run turned out to be sinker, which could be because sinker pitchers are often heavily sinker pitchers, some throwing the pitch up to 70-80% of the time. Out of the 85 at-bats in the sheet that had a slider whiff as whiff one, 45 of the homers were off another slider, while 22 were on fastballs. With the 31 curveball at-bats, there is no real pattern, with the final pitch being a real mixed bag.
There were 34 at-bats that had two whiffs before the home run. 12 of the at-bats were all the same pitch (that is, both whiffs and the home run). 4 of them were sliders, one was all changeups, one was all sinkers, and 6 of them were fastballs. Only three of them were on sequencing with three different pitchers.
As far as individual hitters go, Chris Davis has the most homers that had a whiff with 9. Pedro Alvarez has 7. Mike Napoli, Jarrod Saltalamacchia, Alfonso Soriano, and Justin Upton have 6 and Mark Reynolds, Jason Castro, Adrian Beltre, Chris Carter, and Raul Ibanez have 5. Most of these hitters are batters with power, but have contact problems as well. At least in these at-bats, they both showed up in a matter of a few pitches.
Thanks to Daren Willman of baseballsavant.com for helping me gather the data.