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Clayton Kershaw and tunnels: An initial investigation

Baseball Prospectus’s new pitching data is fascinating, and like always, the Dodgers ace makes them even more so.

MLB: NLCS-Los Angeles Dodgers at Chicago Cubs Jon Durr-USA TODAY Sports

If you haven’t read or perused the articles and leaderboards of Baseball Prospectus’s new pitching stats, hie thee hence. For the first time in the public domain, we now have rigorous methods of measuring such things as command, control, sequencing, deception, and stuff. The data is still raw and analysis of it is still in utero, but the implications are massive.

Disclosure: I am a Dodgers fan. I am also a pitching fan. So the first question I tend to ask when confronted with new pitching data is, “What does this mean for Clayton Kershaw?” The Dodgers ace is probably already a first-ballot Hall-of-Famer and the greatest arm of his generation. He is an outlier among outliers. Be that as it may, his performance within these new metrics might point toward not only how Kershaw finds success, but if there’s anything that could point the future success of other players.

First, let’s define some terms:

Called Strike Probability (CS Prob): This is BP’s way of measuring control. Using the mixed modeling methodology behind their measurement of catcher framing and pitchers’ Deserved Run Average, CS Prob adjusts for batter and pitcher handedness, pitch location, pitch type, and count to measure how likely a pitch is going to be called for a strike. CS Prob doesn’t go by the rulebook zone, but rather by the dynamic zone that tends to get called in practice.

Called Strikes Above Average (CSAA): BP already rolled out a version of CSAA two years ago in order to measure a catcher’s pitch framing skill. This pitcher version flips it around to control for the catcher’s effect to see how many extra called strikes a pitcher gets on the edges of the zone. If they are getting more than the average pitcher, that indicates that their ability to hit locations is strong.

Pitch Tunnels: We’ll be spending most of our time with these numbers. In essence, tunnels measure sequencing, deception, and “stuff” in multiple ways. There is a point in the flight of a pitch that a batter must decide whether and where to swing. If a pitcher can disguise his pitches up to that point, he will fool hitters. Or, if a pitcher has great stuff that isn’t easy for a hitter to manage, then he can use the tunnel point to keep a hitter off balance, even if they know what pitch is coming. There are several measurements under the “tunnel” umbrella, so we’ll go one-by-one as they come up.

So, how does Kershaw perform in all of these metrics? Last year, Kershaw’s pitches were 49.65% more likely to called strikes than the average pitcher’s. That made him the 10th-best control pitcher among starters who threw at least 100 innings. That’s very good! The eye test confirms Kershaw’s ability to pound the zone with his fastball, while also being able to drop in his breaking balls for strikes.

So Kershaw was the 10th-best starter by control last year. Who was ninth? Shelby Miller. Mike Foltynewicz was sixth. Jimmy Nelson was third. Rob Mains ran a study to find any relationship between control and DRA, and found very little. Control in a vacuum doesn’t seem to suggest much.

Let’s pivot to command. Mains’s study suggested a stronger relationship to DRA, though as a predictive tool for individual pitchers, it may be weaker. Kershaw’s CSAA last year was a fairly pedestrian 0.22%, tied with Adam Conley and Ian Kennedy in the middle of the pack. This is somewhat surprising, given Kerhsaw’s reputation for putting the ball wherever he wants. On further reflection, his pitches—especially his slider—have such crazy break that hitters are fooled by them long before anyone knows where the pitch is going to complete its journey.

So that leads us to tunnels. Each of these metrics are measured by comparing the differences in pitches thrown back-to-back—in other words, sequences. I took a look at the 162 pitchers who through at least 1,000 pitch pairs last season. How does Kershaw do?

Tunnel Differential measures how much the ball changes its flight path after the tunnel point (23.8 feet before home plate). If the differential is big, then the pitches are far apart. To add to the “no one size fits all” craziness to these numbers, a large tunnel differential could be bad, or it could be good. For Kyle Hendricks, a small tunnel differential means that pitches don’t know what pitch is coming. For Rich Hill, a massive tunnel differential means that his curveball is breaking all over the place, and hitters can’t deal with its movement.

Kershaw’s tunnel differential comes in at 0.8553, 56th out of those 162 pitchers. His pitches don’t really look the same once they hit the tunnel point. He’s not as extreme as Hill or Adam Wainwright, but he’s not really hiding what’s coming.

Plate Differential measures where two pitches end up as they cross the plate. If the gap is big, then there may be command issues. If the gap is small, then pitches are all going to the same area of the batter’s box. Kershaw ranks 110th with a 1.5246 Plate Differential score. his pitches are generally going to the same area! Given his middling command and his large tunnel differential, one might think that Kershaw would be fairly predictable.

Release Differential basically measures the change in release point from one to the next. If you’ve got a big differential here, then you’re tipping pitches. Kershaw’s 0.2524 score ranks 26th. That’s pretty high!

So too is his Release-to-Tunnel Ratio, which calculates the spread of the release differential to the tunnel differential. Unsurprisingly, Kershaw’s is sizable, as he comes in at 28th. He’s not hiding his pitches much.

Post-Tunnel Break is basically what it sounds like: How much does a pitch’s movement change after it passes the tunnel point? Shock of shocks, Kerhsaw’s 0.448 mark was the best in baseball last year. Anyone who’s ever seen Kershaw drop his hammer curve or his tight slight slider into a batter’s path knows how much movement he gets on those pitches. What is extremely revealing is that this kind of movement happens mostly after the tunnel point, so batters, while they may be able to tell what’s coming by the tunnel point, can’t really catch up to the pitch.

Kershaw also rates extremely well by Flight Time Differential. How much does a pitcher change speeds between pitches? Kershaw does it a lot, as his 0.0427 Flight Time Differential was sixth last year. If a pitcher is teed up for a 94-mph fastball and then gets a 73-mph curveball with tons of late movement, there’s no hope.

Finally, Break-to-Tunnel Ratio measures Post-Tunnel Break against Tunnel Differential. How much is a pitcher’s movement closing the gap, potentially, with a rather large Tunnel Differential? Kershaw kills it in this area. He makes up for that large split between pitches at the tunnel point by having tons of late movement. His 0.5238 Break-to-Tunnel Ratio was second in baseball last year.

Some early conclusions: Kershaw varies his release points and doesn’t disguise pitches before they reach the tunnel point. His pitches also finish in generally the same spots. However, by pounding the zone, adding crazy movement, and switching up speeds, hitters remain heavily off-balance, even if they know what pitch is coming and where it might finish after it crosses the plate.

In their article, “Two Ways to Tunnel,” authors Jonathan Judge, Jeff Long, and Harry Pavlidis present the contrasting paths of Greg Maddux and Barry Zito. Through a combination of command, crafty sequencing and disguise of his pitches, Maddux owned hitters’ souls. Kyle Hendricks would be a modern comp. Zito, on the other hand, used raw stuff that broke in all kinds of directions to overpower hitters. Kershaw would seem to fit this mold, but perhaps even more efficiently than Zito ever could.

Might Zito’s decline be a cautionary tale for Kershaw? Perhaps. Improving command is often thought of as an older player skill, much like pulling the ball and drawing more walks would be for hitters. Kershaw could go a more Maddux route as he ages, to offset a decline in fastball velocity and a fading crispness in his breaking pitches.

On the other hand, Kershaw might be such an extreme outlier that his stuff will never lose its bite. Kershaw is a fiercely intelligent pitcher, and one would be wise not to second-guess him. It is clear, however, that he doesn’t need no stinking finesse in order to pile up strikeouts, never walk a guy, and never let batted balls hurt him. He is the special one.