Better Stats for Finding the Next Rhys Hoskins

Carson had an interesting article about finding contact hitters who can elevate. That makes a lot of sense, especially if the ball is really juiced, because that new environment means that more FBs are going out even though they are not totally crushed. A couple months ago I already correlated power and contact together with walks, and had pretty decent correlations with performance. Power and contact together is definitely a good thing. However, when it comes to low-minors players, often the power is not present yet, so it can make sense to look at the batted-ball profile instead when evaluating potential for growth.

Now, that is not a hard rule, and you could actually say that a strong ground-ball hitter like Daniel Murphy when he was young has actually more potential for growth than a weak FB hitter when he actually learns to elevate, and he and others have shown that it is possible to make that change even in the late 20s, but we also know that sustainable swing changes are quite hard to attain (there are the Murphys and Donaldsons but also guys like Jason Heyward who tinker with the swing every year and make it worse because muscle memory gets confused), and it is probably a safer bet that a young minor leaguer (17-19-year-olds especially) can add some muscle and make some of the FBs go over the wall.

Instead of FBs, however, I have tried a new stat. Instead of FB% I have used a stat I called “effective off the ground percentage.” I used off the ground percentage because line drives are just as good as FBs (actually better) and everything off the ground is good unless it is a pop-up. Basically it is 100 minus GB% minus PU% (IFFB*FB/100). I think that is important because pop-ups are a terrible result and we do know that extreme FB hitters like Schimpf, Story, or Odor tend to have elevated pop-up rates. Overall, there is a small but not super significant positive correlation between FB% and IFFB% (0.3 Pearsson), but at the extreme top end of launch angle, the pop-ups do get higher.

That means, obviously, a hitter who can get the ball off the ground while avoiding pop-ups (like Trout or Votto) is a big asset. Still, the overall correlation of wRC+ and effective off the ground percentage is not huge, although it is better than just FB% (0.23, vs 0.17 Pearsson).

The effect gets stronger at the extreme ends; for example, the top-20 in effective off the ground percentage is at a 117 wRC+ and the bottom 20 just at 99. However, of course power still plays a big role, as do strikeouts. Launch angle does help, but there are limits to that; it is not a magic pill. The most important things are still the big three — power, contact, and plate discipline. But a bad batted-ball profile can make the other peripherals play down. There is an effect of diminishing returns. Getting balls in the air is good, but it is mostly an issue when it gets extreme. If you have 6-degree LA/50% grounders, that is bad, but once you get past average (10 degrees, 45% grounders) there is not that much of a gain by further increasing LA.

I don’t believe in that “steeper swings lead to more Ks” thing, but higher LA can have a cost of BABIP and sometimes pop-ups. So I’m not sure a Hoskins / Jay Bruce / Cody Bellinger FB profile is that much better than a normal 40% FB profile. In the end, there is a threshold when LA can’t be further increased.

The FB revolution is mostly helping the guys who had extreme grounder profiles; in the end, it is probably best to have a slightly above-average LA of like 12 degrees, and have an off the ground percentage of 60+%, but extreme FB profiles probably only make sense for extreme power guys.

Carson’s article had Rhys Hoskins in it, but also Willians Astudillo, who probably won’t become a star. I think it is good to look for prospects who don’t hit on the ground too much, but I’m OK if my prospect hits like 45% grounders since many prospects tend to improve that a little in the majors, and I don’t think looking for extreme off the ground profiles brings that much of an extra advantage.

However, when a guy hits a ton of grounders, it is a red flag, especially if it comes with K issues. If you can’t make contact better, make your contact count with hard-hit fly balls. Moncada has that problem somewhat, and needs to improve that.

However, what is also bad is pop-ups with no power. J.P. Crawford, for example, has good off the ground rates (almost 60%) but also insane pop-up rates. He is starting to develop some pop, but unless it gets better, he probably might be a low-BABIP guy. He probably might be better off with a more conservative batted-ball profile of like 45% grounders and a little less pop-ups, so that his BABIP gets better. His off the ground rate is 60% but his effective off the ground rate is actually slightly under 50%, which means he is not getting the benefit of staying off the ground, but is paying the costs.

Of course, his plate discipline and contact profile would still work with average power, but the batted-ball profile definitely is not ideal.



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Jim Melichar
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Prior to having the minor league batted ball data this year, I previously looked a lot at the SLG% for AA as a proxy for how high a player might be able to reach in the majors. I used that for about a decade or so when trying to quantify ceiling for fantasy baseball prospects (along with their prospect grades for power of course).

I’m glad we have a much richer set of data to play with now.