The Change: Kang, Yelich and Batted Ball Changers

Ground-ball rate stabilizes fairly quickly. Usually, you’ll hear this factoid in the first month of the season as we look at April stats and try to render prognoses on the rest of the season. Of course, ‘stabilizing’ means that there’s about a 50/50 chance the data is meaningful in that small sample.

Hidden in that fact is the key to today’s look at the player population. Players change. They change their batted ball mixes in season, too, not just in April. And if you look at month-long samples, you’re pretty close to that stabilization point again. You want about 30 games to believe in ground ball numbers, and your qualified batters typically play around 25 games in a month.

And, since we’re now comparing July to June instead of April to all of last year, and we’ve already admitted that players change their mixes, it’s useful to remember that this is not some sort of skeleton key that will figure it all out for us. Still, we need to know which players are altering their batted ball mixes, because it might stick, and it might mean something going forward.

And for Christian Yelich, Adam Eaton, Brandon Crawford and even Jung-ho Kang… we could be seeing the future.

Let’s look at the hitters that have cut their ground-ball rate the most in July. With the veterans, it’s often a regression to career means. But the young guys? They are particularly interesting.

(The average ISO is ~.145, and the average pop-up rate is ~3.5%.)

Name	July BABIP	July ISO	July GB%	June GB%	May GB%	July-Jun GB	July-May GB	June PA	May PA	July PU%	July Hard%
Robinson Cano	.342	.286	38.6%	56.4%	51.7%	-17.8%	-13.1%	104	114	1.2%	39.8%
Christian Yelich	.360	.110	57.3%	74.0%	63.0%	-16.7%	-5.7%	105	85	0.0%	32.5%
Brian McCann	.217	.206	22.0%	38.3%	38.9%	-16.3%	-16.9%	86	99	6.0%	34.0%
Mike Moustakas	.178	.118	30.7%	45.3%	53.3%	-14.6%	-22.6%	107	92	6.7%	39.0%
Yonder Alonso	.235	.113	38.6%	51.9%	25.0%	-13.3%	13.6%	105	18	4.3%	22.9%
Elvis Andrus	.316	.101	40.5%	53.8%	37.8%	-13.3%	2.7%	105	128	1.4%	34.2%
Angel Pagan	.329	.034	34.2%	47.5%	48.9%	-13.3%	-14.7%	105	106	0.0%	21.9%
Adam Eaton	.391	.216	38.4%	51.3%	51.8%	-12.9%	-13.4%	111	117	2.7%	26.7%
Kolten Wong	.275	.080	35.4%	48.1%	43.3%	-12.7%	-7.9%	106	121	3.7%	30.5%
Mark Teixeira	.345	.391	26.9%	38.2%	51.9%	-11.3%	-25.0%	101	107	3.0%	44.8%
Brandon Crawford	.258	.259	41.8%	52.9%	45.9%	-11.1%	-4.1%	104	114	0.0%	32.4%
Jimmy Rollins	.215	.247	33.3%	44.4%	41.3%	-11.1%	-8.0%	101	108	7.3%	30.4%
Erick Aybar	.353	.079	46.3%	57.0%	54.1%	-10.7%	-7.8%	103	113	3.7%	20.9%
Freddy Galvis	.377	.165	32.9%	43.5%	41.9%	-10.6%	-9.0%	88	106	4.3%	31.0%
Chase Headley	.439	.111	34.3%	44.7%	50.0%	-10.4%	-15.7%	119	113	10.4%	19.4%

Before he signed with Seattle, Robinson Cano hadn’t hit more than 50% ground-balls since 2007. His man muscles had made him a power hitter and he was going to hit fly balls to take advantage of that fact. Then he hit Seattle. Then came all the ground balls. This has to be seen as good news — he’s back to the power-hitting profile. His July isolated slugging number suggests that it’s been a success.

Sometimes you write about how Brian McCann has cut the pop-ups and then he has a month in which he cuts his ground-ball rate in half and doubles his pop-up rate. That’s the danger of these things — even if you line up player comments with current numbers, it’s almost impossible to really nail when change is meaningful.

Still, Brian McCann has been around a while. Ditto Elvis Andrus (who really shouldn’t be hitting fly balls anyway) and Mark Teixera. Jimmy Rollins has rediscovered his mojo recently, and his current month ground-ball rate resembles his best power years, so that might be a good sign. Or he might just regress to the 40% ground-ball rate that he’s shown for most of his career. Okay, he’ll probably do that.

On the other side of the coin, we have the young guys.

If you listen to the podcast, you may have noticed me railing against Christian Yelich. Despite wanting him to be a new Jason Heyward, and despite the fact that hitters generally cut their ground-ball rate as they age, Yelich has been pounding the ball into the ground at a legendary rate, especially for his kind of player. Count this as great news then: July’s 57% ground-ball rate represents only the third time that Yelich has hit fewer than 60% ground balls, but those three months have all come since June of 2014. Even if he could cut his ground-ball rate to 55% going forward, he’d be more comfortable surrounded by Adam Eaton and Wilson Ramos in the category instead of sitting next to the punchless Nori Aoki, Ben Revere, and Dee Gordon.

Speaking of Adam Eaton, his recent power surge has a source, and that source is hitting the ball on the ground less. Though Eaton has some speed and can get on base, he’s probably not the kind of guy that should slap the ball into the ground and fly. Being a 15/15 guy would be better for his value in both real and fantasy baseball, and it sounds like he’s finally figuring that out. He’s gradually cut his ground-ball rate in every month, and this seems organic and sustainable.

I’d actually count the July fly ball rate as a step back for Mike Moustakas, as his worst batting averages on balls in play have come when he was hitting everything in the air. This might not be good news. Angel Pagan hitting a lot of fly balls with marginal power in a bad stadium also seems like a bad idea.

But for Kolten Wong and Brandon Crawford, it might mean that these two middle infielders are growing into their power. It’s a little more clear-cut for Wong, who has been surprising us with his power for a while, and has been cutting the ground-ball rate in fits and spurts as he takes advantage. The isolated slugging percentage on that month shouldn’t worry you too much — more fly balls should eventually mean more home runs for him.

Crawford is a little bit older than Wong — 28 to his 25 — but you can see the same ground-ball change within the Giants’ middle infielder. It looks like he’s slowly trusted himself to hit the ball in the air more. Last year was his lowest ground-ball rate and his highest isolated slugging percentage of his career, and that’s no coincidence. This seems to suggest that his new-found power level is sustainable.

Not pictured, but worth mentioning, is one last middle infielder. Jung-ho Kang has seen regular playing time, and his stats have changed in an underlying way, even as he continues to show power and speed and decent plate discipline and contact skills. He was hitting a ton of ground-balls early on, and even if he didn’t think it was a big deal, he has reversed that course recently. His May ground-ball rate was 58%, in June it was 50%, and last month it was 45%. Look at his yearly total, at 50%, and you may think there isn’t much power upside left. Here’s an analyst saying that he has more power potential left, based on swing mechanics and these batted ball mix changes.

The less information you have about a player’s career, the more you should be looking at peripheral stats like these. Kang may not be a rookie, but we don’t yet know exactly what his true talent power looks like. So, along with Wong, Crawford, Yelich, and Eaton, we can see that fewer ground balls in July is something worth noticing.