Here’s an Astonishing Clayton Kershaw Statistic

Clayton Kershaw is an outlier, and for the more number-oriented among us, outliers can be best appreciated through their statistics. One could investigate Kershaw with the same enthusiasm with which one could investigate Barry Bonds. Maybe more fittingly, he’s like a modern-day Pedro Martinez. His career could be considered an accumulation of incredible fun facts. There’s the one about how his five-year ERA is still holding under 2.00. There’s the one about how Kershaw allowed an identical .521 OPS in three consecutive seasons. (In the fourth season, Kershaw got better.) It’s overwhelming to think about gathering all the best Kershaw fun facts. There are too many. You might already have your own favorite.

Now I have another fact to add to the list. It’s a little bit different — it’s as much about the hitters as it is about Kershaw himself, and it isn’t even necessarily good. What it is is an outlier. It’s another Kershaw stat that stands out from the pack. It requires some digging to get to, but the effort, I think, is worthwhile, because seldom do you ever encounter such statistical separation.

Posts like this should probably have a default credit button that links out to Baseball Savant. That’s where much of this information comes from; that’s where much of *all* baseball information comes from. To work toward the stat in question, I think we need to build up. Kershaw has pitched his entire big-league career within the pitch-tracking era. That’s convenient! This season, he’s started 18 games. As such, I’ve prepared some career-spanning 18-game rolling averages. Here’s the first one, showing Kershaw’s progressive rates of pitches thrown while behind in the count. So that we’re absolutely clear, these are, say, 1-and-0 pitches, or 2-and-0 pitches. Pitches when the hitter has had an advantage, at least relatively speaking.

This is probably about what you’d figure. Kershaw has gotten better and better over time, especially when you think back to his earlier, wilder days. Effective pitching is really about two things: finishing hitters off, but also getting into situations where they can be finished off in the first place. The more a pitcher gets ahead, the less often the pitcher falls behind. No pitcher wants to fall behind. Kershaw rarely does. He’s as much in control as anyone else. More so, to be honest.

Now let’s focus *just* on the pitches Kershaw has thrown while behind. So we’re eliminating even counts, and pitcher-friendly counts. Here are Kershaw’s rates of those pitches that wound up within the Gameday strike zone:

Kershaw, for a while, has pitched pretty aggressively, here. When behind, he’s routinely thrown something like 60% of his pitches in the zone, and there was an even higher recent uptick. Kershaw’s rate has consistently been higher than average; just about every pitcher wants or needs to throw more strikes when behind, but Kershaw’s done it without concern. He’s worked hard to get back even. He hasn’t tried to get too many hitters to chase.

That being said, we can also look at Kershaw’s fastball rates while behind. One typically associates hitter-friendly counts with fastballs. And, as a general rule, that’s fair! Kershaw, though, has been straying.

Kershaw used to throw an extremely high rate of fastballs when behind. More recently, he’s been only a little over 50%. You might recall that fun fact about how Kershaw just about never throws a curveball when he’s behind. That’s still true. The curveball only shows up under other circumstances. But Kershaw has reduced his hitter-count fastball usage, while greatly boosting his usage of sliders. So far this season, it’s been about 50/50.

At last, we get to about where we’re going. When Kershaw has fallen behind, he’s been aggressive, in terms of throwing strikes. He’s been *less* aggressive, in terms of throwing fastballs, but even there, he’s been more like a two-pitch pitcher, instead of a three-pitch pitcher. How have hitters responded? Here are rolling swing rates when Kershaw has been behind, or, if you prefer, when those hitters have been ahead:

Hitters have gotten more and more aggressive. You can’t fully appreciate this yet, because I haven’t established any context. This isn’t a stat we commonly look at, so you don’t have a frame of reference. Don’t worry, we’ll get to that. I have a highly informative table! But just before that, here’s another look at Kershaw’s career, this time separating by season. You see swing rates when Kershaw has been behind, and you see combined swing rates when Kershaw has been even or ahead.

There’s developing separation. Even last year, Kershaw had an above-average swing rate in other counts, while having the No. 1 swing rate while behind. This year, Kershaw’s swing rate in other counts ranks in the 65th percentile. But he once again has the No. 1 swing rate while behind. And he’s not just No. 1. Check out this ridiculous top 10.

There it is. There’s our astonishing Kershaw fact. When Kershaw has thrown a pitch while behind this season, hitters have swung more than 64% of the time. That’s the highest rate in the game, by nearly eight percentage points. Look at the spread between Kershaw and Stammen. Look at the spread between Stammen and Bradley. As another way of understanding this, Kershaw’s swing rate here is higher than the average by very nearly four standard deviations. Anything that’s so far from the average is a statistical absurdity. It took work to get to this, but that doesn’t make it any less insane. Hitters have lost their minds trying to make Kershaw pay when they’ve had the chance. It’s not that it’s the wrong idea. It’s that it’s the idea at all. Hitters know that, when Kershaw gets into a decent count, they don’t have much of a chance. And so, far more than ever, Kershaw’s opponents have looked to pounce when they’ve known he’ll be around the zone, throwing one of two pitch types.

Kershaw’s sitting on a 2.19 ERA. That’s his highest since 2012, and he has already allowed a career-high 17 home runs. On the other hand, he’s sitting on a 2.19 ERA, and no opponent has scored an earned run since June 19. It seems like Kershaw might have something to adjust, but I don’t know how much adjusting he truly needs to do. He could, I suppose, stay out of the zone a little more. Or he could, I suppose, elect to mix in a few curveballs here and there. But I’m not going to claim that it’s Kershaw who needs to do the work. I don’t even quite know what to make of this. I just know this reflects the hitters’ collective desperation to do something, anything, when an opportunity is presented. Hitters are more aggressive than ever when ahead against Kershaw, because they know the chance is fleeting. It’s a legitimate adjustment on their part, but it might not require such a dramatic adjustment back. That’s for Kershaw to figure out.

For us, this is just how the game is presently working. Hitters this season have made a real change. Give them credit for that; they’re not giving up. Even after all these years, they’re looking for a way in. Kershaw doesn’t provide very many.