Yandy Diaz and a Potential Swing Change

Since statcast has been added to MLB parks, exit velocities and launch angles have been a hot topic. Some of this is as simple as a players ground ball rates decreasing, while others dive into a little more detail. For example, showing that a player is hitting more balls into the ideal launch angle ranges for batted balls (19-26 degrees). Regardless, it can be hard to keep track of these changes, or to understand what it all means if you are not familiar with the data. Luckily, Andrew Pertpetua put together this primer. You should definitely read it if you have not already. As Andrew notes, there are a few takeaways.

  1. Exit Velocity is more predictive than launch angle in terms of measuring success.
  2. Exit Velocity peaks between -10 and 10 degrees.

This follows along with what we should intuitively expect. The harder a player hits the ball, the more likely he is to be making good contact, which should lead to better expected results. Certainly, this isn’t an absolute, but it’s an okay starting point. The less directly a ball is hit – positive or negative launch angles – the greater a sacrifice in exit velocity we would expect to see, at the benefit of a potentially more ideal launch angle.

Below, I have included a table of exit velocity z scores 2017 and the expected OBA for all players over each cutoff.

Exit Velocity Std Dev
z-score Avg xOBA Avg EV
0.00+ 0.348 89.50
1.00+ 0.379 92.02
1.50+ 0.396 93.33
2.00+ 0.412 94.78
All 0.326 87.52
SOURCE: xstats.org
– Over 30 BIP
– n=375
– Avg EV = 87.52
– Variance = 8.33
– Std Dev = 2.89

We would expect some great players to be included near the top of this list if their expected OBA (on wOBA scale) is near .400.  This leads to the following question. Is there anyone displaying well above average exit velocity who is making less than ideal contact? What I mean by this is not, “who would see the greatest improvement in results if they did increase their launch angle?” But rather, who are some players who are hitting the ball hard, but may not be hitting the ball at launch angles that will maximize their results. While making changes in life of any kind can be difficult, my presumption is that if you show the ability to hit the ball with well above average exit velocity, making a change to increase loft in your swing plane (and the impacts of this) will be less likely to cause exit velocity to fall into a below average range. Below is our exit velocity leaderboard for players with 30 batted balls.

1.5+ Z-Score Group based on  Exit Velocity
Name xOBA xOBA+ avg EV Vertical Spray
Miguel Sano 0.397 124.8 97.9 19.1 -3.1
Aaron Judge 0.432 135.7 94.4 11 -5.1
Alex Avila 0.512 161 94.4 18.2 7.1
Adam Lind 0.411 129.2 93.7 11.4 7
Yandy Diaz 0.270 84.8 93.7 -3.5 7.1
Manny Machado 0.377 118.5 93.6 12.9 -5
J. D. Martinez 0.504 158.6 93.4 13.4 -3.1
Joc Pederson 0.277 87.1 93.2 9.2 19.5
Khris Davis 0.376 118.3 93.2 12.1 5.1
Miguel Cabrera 0.433 136 93.2 11.4 9.1
Joey Gallo 0.356 111.8 93 26.4 18.7
Paul Goldschmidt 0.484 152 92.9 14.1 -0.6
Chad Pinder 0.363 114.2 92.9 21.6 4
Justin Bour 0.363 114.2 92.6 9.1 12.1
Ryan Zimmerman 0.414 130.2 92.6 10.2 2.4
Gary Sanchez 0.342 107.4 92.5 13.9 -13.9
Yasmany Tomas 0.347 109.1 92.4 8.2 2.2
Freddie Freeman 0.440 138.2 91.9 14.6 9.7
Nelson Cruz 0.379 119.2 91.9 12.4 5
SOURCE: xstats.org
30 batted balls needed for inclusion

There are a couple of names that immediately stick out. The first, and perhaps least surprising, is Miguel Sano, followed immediately by Aaron Judge. Both of these players hit the ball hard.  However, near the top of the list also sits Yandy Diaz and Joc Pederson. I want to touch on Yandy today. While Adam Lind and Alex Avila could also garner attention as names that stick out at the very top, Yandy is the only player with an average exit velocity over 1.5 standard deviations from the mean with an expected OBA below .370, and he is 100 points lower than that at .270. A likely reason for this is that his average launch angle on all batted ball types is below 0, at -3.5 degrees. For reference, the expected outcomes on balls of this type are as follows.

Launch Angle Below Zero Degrees
138,986 26,910 24,854 1,956 100 0 .194 .194 .209 .194 .194 .176
SOURCE: xstats.org
– classified as dribble balls
Launch Angle between 0 and 10 degrees
49802 23686 21478 2108 100 0 .476 .476 .522 .476 .476 .436
SOURCE: xstats.org
-classified as ground balls

When nearly 50% of all batted balls are these dribble balls – ground balls under zero degree launch angle – it’s difficult to take advantage of the near elite exit velocity he is displaying. While ground balls have legitimate value, once you dip into the negative launch angle bucket, it is difficult to capitalize on elite exit velocity. While the ball is hit with a lot of force, it is likely in contact with the ground for a much longer period of time before it reaches a fielder, causing it to slow down. Let’s dig a little deeper into his batted ball types.

Yandy Diaz Batted Balls
Lg Avg EV BIP Avg EV Vertical Spray
Total 87.1 48 93.7 -3.5 7.1
x<0 81.6 24 90.0 -23.1 2.8
0-10 93.0 13 102.3 5.2 6.2
10-19 92.8 5 102.2 15.0 14.1
19-26 91.9 1 87.6 20.2 25.7
26-39 89.8 3 89.9 33.3 7.3
x>39 83.5 2 69.9 61.2 36.5
SOURCE: xstats.org

Of his 48 balls in play, nearly 77% are balls hit under 10 degrees. However, what I would notice here is his exit velocity on each batted ball type. While sample sizes will be an issue, he displays above average to well above average exit velocities on each batted ball type with the exclusions being balls hit over 19 degrees (he has only put six balls in play over 19 degrees all year).

The takeaway from this is that Yandy would likely benefit from altering his swing path slightly in an effort to minimize the large portion of his batted balls that fall into the “dribble ball” range. While he doesn’t need to go full Yonder Alonso in order to be an effective player, even a minor change in this area could boost him into a useful platoon outfielder or third basemen in deeper fantasy leagues.

The other name on this list that I have not mentioned is Joc Pederson. I will touch on him next week. Are there any names that stick out as names for potential swing changers?

Joe works at a consulting firm in Pittsburgh. When he isn't working or studying for actuarial exams, he focuses on baseball. He also writes @thepointofpgh. Follow him on twitter @Ottoneutrades

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You can’t assume that a change in bat path wouldn’t wreck his exit velocities. It is his current swing that generates the contact you are describing, not a hypothetical one which may or may not exist. If he is going to increase his launch angles, then he may as well press turbo for a 2 MPH boost to all batted ball types. That is assuming that we are ruling out pressing up, up, down, down, left, right, left, right, B, A, Start on the title screen to enter God mode.

Francis C.
Francis C.

True, but it’s worth a shot. It’s worked for other players.


There is also the chance that his already not-great hit tool turns to mush.

I don’t think you have causality, even if a player attribute his success to it. You see the way that players are lauded for their data-driven approaches or at least for talking about it. Without underlying skill growth, I am not sure that adjustments work so well. How do you know that adjustments aren’t really just the game slowing down, which is what happens when a guy becomes a star? I would be surprised if that isn’t exactly what underlies most swing-revolutionaries.


The counter to what you’re saying though is, what does he have to lose? He was optioned to AAA because of his .203/.268/.219 line and them having better options. there’s not that much more to fall if the swing change fails, but your upside is potentially dramatic.

To your point in your second post, it feels a bit naive to attribute it to something else. If you have a state where you have trouble hitting, intentionally work on altering your swing path, and then have much more success, what else would be the driver?

As a AAAA player at best, what do you have to lose?