Pitch Speed and Quality of Contact

I don’t spend a lot of time thinking about the Marlins, but of the time I do spend thinking about the Marlins, the bulk of it is spent thinking about that one home run Giancarlo Stanton blasted off Jamie Moyer. You know the one — the one that broke the scoreboard, the one that set an ESPN Home Run Tracker speed-off-bat record. The home run, just fair, was also a grand slam, and it was the hardest-hit home run baseball’s seen in at least seven years. Stanton didn’t catch up to a blazing heater. This was Jamie Moyer, after all. Stanton ripped a full-count changeup at 72 miles per hour.

There exists some sentiment that harder throwers will give up harder contact than softer throwers. Less contact, of course, but also harder contact. The idea is that Aroldis Chapman‘s balls in play will be struck harder than Livan Hernandez’s balls in play. It’s based in very simple physics: we care about the velocity of the ball, the mass of the ball, the velocity of the bat, and the mass of the bat. Hold everything else constant and, as you increase the ball’s velocity, you end up with a greater speed off the bat. The reality is more complicated than this, but this gets to the core.

Yet this is a tricky thing to observe. We don’t see harder throwers posting unusually high home run/fly ball rates. We don’t see faster pitches leading to elevated BABIPs. I got curious about something that I’m sure others have already investigated, but I wanted to look at the slowest pitches and the fastest pitches hit for home runs during the PITCHf/x Era. President Appelman gifted me with a log of every home run hit over the last five years. Included was the corresponding PITCHf/x pitch speed, and I isolated the top and bottom 150. 150 was basically an arbitrary cutoff. Here’s a graph showing the difference between the two groups of dingers:

Group 1 includes homers hit off pitches with an average speed of 66.0 miles per hour, +/- 2.7. Group 2 includes homers hit off pitches with an average speed of 97.7 miles per hour, +/- 0.8. Obviously, these two groups are significantly different — the average pitch in Group 2 was 48% faster than the average pitch in Group 1. Many of the pitches we see in Group 1 happen to have been thrown by Tim Wakefield. As a matter of fact, just under half of the pitches we see in Group 1 were thrown by Tim Wakefield.

Dingers identified and isolated, I then tracked them all down on the ESPN Home Run Tracker and made note of their listed speeds off the bat. This is more or less why I used a 150 cutoff — a bigger sample meant more manual labor. I didn’t go in with any expectations, and I was curious what my resulting graph would show. Here is the resulting graph, showing speed off bat, broken down into the two groups:

There’s nothing there to be found. The average speed off bat for a homer in Group 1 is 103.2 miles per hour, +/- 4.7. The average speed off bat for a homer in Group 2 is 103.3 miles per hour, +/- 4.3. Last season, the league-average speed off bat for a homer was 103.4 miles per hour. That hasn’t really changed since 2008.

The results are virtually identical. The slowest pitches hit for home runs came off the bat the same as the fastest pitches hit for home runs, at least in terms of speed. I didn’t check distance or launch angle, because I was most interested in the one number I noted. The fastest pitch hit for a home run was hit by Tyler Greene off Andrew Cashner in May 2012, and it left the bat at a recorded 101.2 miles per hour. The slowest pitch hit for a home run was hit by Ike Davis off Vicente Padilla in July 2010, and it left the bat at a recorded 102.7 miles per hour. The Cashner pitch was 47.4 miles per hour faster than the Padilla pitch.

Because I’m not a physicist, I can’t talk a whole lot about these results. It’s long been clear that bat speed makes a substantially bigger difference than pitch speed, simply because a bat is a lot more massive than a baseball. Yet pitch speed should matter, if you hold everything else constant. So one wonders if everything is truly being held constant. The faster the pitch, the less time the hitter has to react, so the less time the hitter has to get his bat to peak speed. What we might be seeing is reduced bat speed offsetting increased pitch speed. We know it’s more difficult to make contact with a faster pitch; we might infer that it’s also more difficult to make good contact with a faster pitch, perhaps because bat speed is lower. It seems intuitive to me, but I haven’t been a scientist for years. These days I’m just a guy who’s writing this blog post.

The slowest pitches hit for home runs have been hit just as well as the fastest pitches hit for home runs. There are various scientific concerns, and sample-size concerns, and selectivity concerns as well, since I’m selecting for home runs instead of looking at all balls in play. But Aroldis Chapman shouldn’t be considered a threat to allow a home run because he throws 100 miles per hour. Aroldis Chapman should be considered a threat to allow a home run because he’s a pitcher, and sometimes pitchers allow home runs.