Clayton Kershaw’s Replacing Strikeouts with Strikeouts, Basically

Clayton Kershaw’s good! Here’s something I bet you didn’t know about him. In the first half of this season, he struck out more than a third of all the hitters he faced. In the second half, his strikeout rate is actually down 17%. Now, that’s percent, not percentage points, but it means one of six strikeout victims hasn’t been a strikeout victim. That seems like the kind of thing that should raise eyebrows. But you haven’t noticed because in the first half Kershaw allowed 19 runs, and in the second half he’s allowed 19 runs. One is less inclined to notice when great players are slightly differently great.

Also, his second-half strikeout rate is still extraordinary. Also, he’s still not really walking anybody, even though just yesterday he did put Yusmeiro Petit on base. The regular numbers love second-half Kershaw, but if you dig just a little bit deeper, you can gain a better understanding of how Kershaw has remained so dominant despite giving away a handful of whiffs.

Here’s a clue. From Sunday, Kershaw vs. Andrew Susac:


From the same game, Kershaw vs. Matt Duffy:


You’re looking at a couple of pop-ups. Now, granted, Duffy’s pop-up dropped in between fielders, allowing it to be a run-scoring hit. For Kershaw, that was a bad outcome, but it’s an extremely rare outcome, and all things considered he would’ve been happy with the batted ball. This season, on pop-ups, hitters are batting .021, and slugging .025. They’re almost automatic outs. In the NFL, extra-point success rate hovers around 99%, and more and more people wonder whether the kick should even be necessary. In baseball, a pop-up is a lot like an extra point. The same thing doesn’t always happen, but when it doesn’t happen, it’s highly unusual.

So you know something’s going on with Kershaw and pop-ups. Why don’t we take a look at first- and second-half splits?

1st 34% 4% 8% 0.279 5% 50
2nd 28% 5% 6% 0.252 24% 46

In the first half, Kershaw’s numbers were absurd. In the second half, he’s changed things up a little bit. He’s allowed more contact, but he’s also allowed worse contact, and that pop-up rate is the highest in the major leagues. His first-half pop-up rate was among the league’s lowest. Earlier, Clayton Kershaw was piling up the strikeouts. He’s still getting plenty of strikeouts, but he’s replaced some of them with the ball-in-play equivalent of strikeouts.

By the numbers available on FanGraphs, Kershaw generated three first-half pop-ups — two on May 23, and one on June 13. So, pop-ups accounted for 1.3% of his batted balls. In the second half, he’s had just one start in which he didn’t generate a pop-up, picking up a total of 16 overall. They’ve accounted for 7.5% of his batted balls. That tells you a lot, but we also draw from a conservative data source, and Gameday provides its own classifications.

According to MLB, first-half Kershaw generated ten pop-ups. Second-half Kershaw has generated 31. And, mostly, this has been about righties. Kershaw’s pop-up total against lefties has risen from four to five. His pop-up total against righties has risen from six to 26. That’s an extremely high total, and, where have those pitches been going? You could guess, but we can confirm with the help of Baseball Savant:


Mostly, the pop-ups have come against pitches inside and elevated. And if you examine Kershaw’s pitch patterns, you can see that perhaps this is deliberate. Kershaw has moved more often toward that quadrant.

Looking at his overall pitches against righties:

First half: 22% inside, up
Second half: 29%

Looking at his fastballs, still against righties:

First half: 31% inside, up
Second half: 40%

And how about if we look at first pitches? We’ll look at this two different ways:

First half: 70% inside
Second half: 86%

First half: 27% inside, up
Second half: 45%

More recently, Kershaw has thrown more first-pitch fastballs, and he’s thrown more of them high and tight. In the second half alone, Kershaw has generated 12 first-pitch pop-ups, 11 against righties. The second-place numbers are seven and five, respectively. Kershaw, on the season, has been pounding the zone to open at-bats. Batters, then, want to be aggressive early, because they don’t want to fall behind in the count and have to try to put a bat to Kershaw’s breaking stuff. So with batters looking to swing at 0-0, Kershaw’s moved a little closer to the hands, and more batters have gotten themselves out in a hurry. It’s a somewhat infrequent thing, but all of them add up.

There have been a few elevated breaking balls. Kershaw’s command of his slider is such that he can throw the pitch up and in from time to time, and over the past couple months, Kershaw’s slider has generated seven right-handed pop-ups, against one in the first half. But this is mostly about his fastball — that pop-up total’s risen from four to 17, looking at only right-handed batters. This is what you’d expect. The high, inside fastball is the pop-up pitch, and Kershaw’s thrown more of it. His fastball is also one of those fastballs hitters tend to swing underneath, because of its vertical movement. Kershaw has a long track record of generating pop-ups. They started to go away a little bit when Kershaw slightly altered his approach, but now they’re back with a vengeance, as Kershaw now is blending everything. He’s a strike-thrower like never before. He’s still not allowing much contact. Now he’s also limiting the quality of contact. Kershaw’s simply turned everything up to 11, blending his new skills with his old ones in becoming the perfect pitcher.

So in the first half, Kershaw struck out 34% of batters. In the second half, he’s struck out 28% of batters. But, Duffy’s pop-up aside, let’s go ahead and consider pop-ups automatic outs. That much isn’t always true, but then strikeouts aren’t always automatic outs, themselves. Blending strikeouts and pop-ups, first-half Kershaw turned 37% of batters into easy outs. Second-half Kershaw’s up at 38%. In one sense, the last couple months, Clayton Kershaw’s allowed more contact than he did before. In the truest sense, batters have just found more efficient ways to whiff.

Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

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9 years ago

“on pop-ups, hitters are batting .021, and slugging .025”

This is totally unrelated to the article, but I want to see the infield popup that went for a double.

Spit Ball
9 years ago
Reply to  Jeff Sullivan

That outfield is a weird collection of gifted athletes, high salaries and somewhat underwhelming performance even though they are still quite good. I just don’t know how else to describe them.

Andrelton Simmons
9 years ago
Reply to  Spit Ball

And Sam Holbrook wasn’t umpiring.

9 years ago
Reply to  Spit Ball

I think those are league-wide numbers, not specifically the Dodgers’ allowed line on pop-ups.

Spit Ball
9 years ago
Reply to  Spit Ball

My bad, you are correct.