Batted-Ball Velocity, Adrian Beltre, and Xander Bogaerts

In batted-ball velocity numbers, we’ve got a new toy. It’s hard to know exactly how to use it, as it goes with many new statistical toys. Without even a full year of sample size, we have no idea how accurate the data coming in is, how sticky batted-ball velocity is year to year, or how much of a skill it is. Even worse, the data is incomplete — velocity without angle is somewhat useless, and the angle that’s coming through is only for home runs.

Is there a short-term fix? Is there a way to combine batted-ball velocity with existing stats to make it useful in the short term? I think there might be, and I think the stories of Xander Bogaerts and Adrian Beltre might help us find this patch.

There’s some evidence that velocity stabilizes quickly in-season at least. Jeff Zimmerman found a .51 r-squared after 100 batted balls. In other words, two months of batted ball velocity is enough to tell you more about their future batted-ball velocity than the league-average number.

So let’s split the season into two two-month samples, more or less. Ask the data which batters added the most batted-ball velocity in June, July and August compared to April and May, and you get a tidy list. On that list, Xander Bogaerts is tenth, and Adrian Beltre is 15th. The Red Sox shortstop has added 5 mph to his average batted ball, and Beltre has added 4 mph.

We still don’t know that much more about these two players other than the fact that they are swinging harder. A ball pounded into the ground or straight up in the air can go a million miles an hour and be less effective than 90 mph at the right angle. Take a look at this excellent chart from Alan Nathan, baseball physicist.

Nathan talks often of the donut hole. Look around 90 mph at the purple spot. Those are outs. Soft hits that don’t make it to the outfielders can be hits, and then you want your 90+ mph hits to leave the bat at a 10-20 degree angle, or you want to hit it harder than 95 mph. But 80-90 mph, 20-30 degrees? Those are outs.

Xander Bogaerts (89 mph) and Adrian Beltre (91 mph) are hitting their average ball right at the donut hole in the second half. So why do we care? Well, we might care in one situation and not in the other.

We do have one current stat that approximates batted-ball angle: batted-ball classifications. Obviously it’s not perfect — these classifications are done by human stringers and not by an algorithm — but here in the public sector, it’s what we have. And if we include ground ball, fly ball and line drive information with the batted-ball velocity, a better picture emerges, one that hopefully includes a modicum of angle information.

Batted Ball Velocity Splits with GB/FB Information

Player	Early Velo	Early GB/FB	Late Velo	August GB/FB	Career GB/FB
Xander Bogaerts	84.5	1.92	89.4	2.14	1.35
Adrian Beltre	87.3	1.28	91.3	1.10	1.05
Ryan Zimmerman	90.4	1.63	95.8	0.96	1.22

There’s a bonus player in there, because he fits the Adrian Beltre mold. To try and read between the lines, it looks like Bogaerts is hitting the ball harder, but into the ground. Beltre and Zimmerman, though? They look like they are getting healthy. They’re hitting more fly balls and hitting them harder, and that has to mean something for their improved play recently.

There aren’t many players that have both added four-plus mph and changed their batted-ball mixes much in the past month. Gregor Blanco (1.65 GB/FB early, 1.00 in August, +6.8 mph), Rougned Odor (1.24 GB/FB early, 1.08 in August, +5.2 mph), Andres Blanco (1.37 GB/FB early, 0.82 in August, +4.0 mph) are the only ones to join Zimmerman and Beltre in that regard. If you look down to three mph, Maikel Franco (1.54 GB/FB early, 0.71 GB/FB late, +3.7 mph) joins in a limited sample, and Yasmany Tomas (2.44 GB/FB early, 2.10 GB/FB late, +3.4 mph) looks interesting.

But that last example should give you pause. Look back on the illustration above. If someone is hitting more than two ground balls for every fly ball, it’s possible they are living at the top of the graph. Is an incremental change there worth more or less than an incremental change in the middle of the graph? And what about Yoenis Cespedes, who is averaging nearly 95 mph on all batted balls since the calendar turned to June? It almost looks like it doesn’t matter what angle he has on the ball at that velocity.

We don’t know. We won’t know until we get batted-ball angle on every hit. For now, we can look at the numbers we do have and say, yes, it does look like Adrian Beltre and Ryan Zimmerman are getting healthy. They are hitting the ball harder, and in a direction that looks more like their normal selves.