Fluke watch – Clayton Kershaw

Clayton Kershaw is turning 23 in March. Kershaw has two full seasons under his belt with ERAs under 3.00. Over the last two years, he’s No. 15 in Fangraphs’ WAR. Over the last two years Kershaw has been a very, very good pitcher, with FIPs of 3.12 or better and xFIPs of 3.9 or lower. Moreover, he has been a pretty good strikeout pitcher, punching out more than a batter per inning, and last year he even improved his walk rate to a reasonable level (3.57 BB/9).

Really, the only area that Kershaw has been deficient for the fantasy player has been in the win column due to the failures of his own team. This may still be a problem in 2011, but that’s not Kershaw’s fault.

But how about the parts of Kershaw’s own performance that he can control? Can he continue to keep up that great performance or perhaps even improve further?

Well, let’s take a look at his pitches:

Kershaw’s pitch repertoire

Kershaw broke into the major leagues with only three pitches: a fastball, change-up and curveball. Against same-handed batters (left-handers), Kershaw was solely a fastball-curveball pitcher. Against opposite-handed batters (righties), Kershaw was still mainly a fastball-curveball pitcher, but he mixed in a change-up every so often.

In the start of his second season (2009), Kershaw continued using these pitches in the same manner. But in June of 2009, Kershaw began to use a slider in addition to his curveball. By August, Kershaw had begun to use the slider almost as frequently as the curveball.

In 2010, the change in Kershaw’s repertoire was complete: against same-handed batters, he began to basically stop using the curveball in favor of the slider. Against opposite-handed batters, Kershaw also used the slider more frequently than the curveball, using the slider twice as frequently as the curve (and, actually, he began to use the slider more frequently compared to the curveball as the year went on).

While Kershaw’s fastball usage has been unaffected by the emergence of the slider, Kershaw’s change-up has almost entirely disappeared. Essentially, in 2010 Kershaw was strictly a fastball-slider pitcher against left-handed batters, while he was a fastball-slider-curveball pitcher against right-handed batters.

The movement and velocity of Kershaw’s fastball, curveball, and slider are shown in the tables below (for the purposes of this article, I’m going to ignore the change-up, given that Kershaw used it infrequently in 2008-2009 and basically stopped it using in 2010.):

Year Pitch Type Average Velocity Average Horizontal Spin Deflection Average Vertical Spin Deflection
2008 Fastball 94.37 MPH +2.58 +10.6
2009 Fastball 93.99 MPH +2.92 +12.94
2010 Fastball 92.46 MPH +2.01 +10.98
Year Pitch Type Average Velocity Average Horizontal Spin Deflection Average Vertical Spin Deflection
2008 Curveball 73.53 MPH -3.57 -7.94
2009 Curveball 72.27 MPH -4.05 -7.02
2010 Curveball 73.14 MPH -2.51 -8.93
Year Pitch Type Average Velocity Average Horizontal Spin Deflection Average Vertical Spin Deflection
2009 Slider 80.77 MPH -4.73 +0.64
2010 Slider 81.31 MPH -3.76 -0.16

As you can see, relatively little has changed in Kershaw’s three main pitches over the last three years in terms of how these pitches moved. It should be noted that Kershaw’s fastball has decreased in velocity each of the last two years, by about one mile per hour per year. Kershaw HEAVILY depends upon his fastball, so this bears watching.

If the fastball velocity continues to drop, his results could be greatly affected. This is something to keep an eye on in spring training and April of the upcoming year, though note: Kershaw’s drop in velocity didn’t happen in the ’09-’10 off season, but mainly happened in June of 2010, which makes one wonder about the possibility of injury or something. It could, of course, just be a calibration issue, but keep an eye on this in 2011.

The results of Kershaw’s pitches

Against Left-Handed Batters:

First, as should be obvious from Kershaw’s splits, his pitches are a nightmare for lefties. Kershaw throws the fastball 73.5 percent of the time against left-handed batters, with the slider making up most of the rest of his pitches (24.0%). And that fastball is incredible: Kershaw has gotten a swinging strike rate on the fastball above 14 percent each of the last three years, with it hitting a career high rate of 16.95 percent in 2010.

For reference, the average fastball has a swinging strike rate around 5-6 percent….meaning Kershaw’s fastball gets a swinging strike almost three times more frequently than the average fastball against these batters. That is utterly ridiculous. Kershaw’s fastball has lost its ability to get ground balls against these batters a little bit each year, but the swinging strike rate is so high that it doesn’t matter*.

*How does Kershaw do this? Quite simply, he’s incredibly good at locating his fastball in the up-and-away part of the strike zone, an area likely to get more strikeouts with the fastball. Despite seeming to target this spot, Kershaw does not miss the strike zone very often with this pitch, and the pitch doesn’t miss inside (into the power area of batters) very often either. He is VERY impressive.

Similarly, Kershaw’s slider is terrific against left-handed batters, with swinging strike rates above 20 percent each of the last two years.

All in all, if you have Kershaw and he’s facing a team filled with left-handed bats, you should expect some really good results. Unfortunately, 79 percent of the batters that Kershaw faces each year are right-handed batters.

Against Right-Handed Batters

Against right-handed batters, Kershaw has become a fastball-slider-curve ball pitcher, as mentioned above, with the change-up being used on rare occasions. Since the change-up has become basically irrelevant (he threw 29 total the last four months of the season), I’m going to ignore it here.

Once again, Kershaw is primarily a fastball pitcher, using the pitch over 70% of the time. His aim with this pitch doesn’t seem as specific as it is against left-handed batters; the pitch is aimed on the inside part of the plate (similar to his spot against left-handed batters), though it does hit the middle of the plate a bit. As against left-handed batters, the pitch is primarily aimed high in the strike zone, but not too high…the pitch is still in the strike zone very frequently (more on this in a bit).

The end result of this aim is that the fastball’s results are much closer to average against righties than against lefties. The pitch’s swinging strike rate actually decreased to a career low in 2010, down from 7.6 percent in 2009 to 5.8 percent in 2010, essentially making the pitch go from above average at getting whiffs (by a little bit) to barely below average.

The pitch’s groundball rate (43.7 percent) in 2010 was above average, but Kershaw’s GB rate on this pitch has fluctuated each year (from 45.0 percent to 39.7 percent to 43.7 percent), so it’s likely this is just a random result rather than a true change.

All in all, however, the fastball was still a pretty good pitch against these batters, even when you take into account BABIP and HR/FB oddities. It is, however, not as insane a pitch as it is against left-handed batters.

The slider was a revelation for Kershaw against right-handed batters in 2010. Traditionally, a slider is a pitch used mainly against same-handed batters, with the change-up taking its place against opposite-handed batters. Alternatively, you’ll see pitchers use a curveball instead to handle opposite-handed batters.

Kershaw, on the other hand, has marginalized his change-up and begun to use the slider against opposite- (right-) handed batters, as opposed to what you’d expect. And, in fact, after a rough start with this pitch in 2009, it was tremendously successful in 2010.

In 2010, the swinging strike percentage of the pitch against right-handers increased to 17.7 percent from 11.0 percent, and the groundball rate improved from 18 percent to 33 percent (though, admittedly, the 18 percent result in 2009 was based upon only 11 batted balls and was probably just bad luck).

The end result is that the slider has given Kershaw a second deadly weapon that he uses most frequently in two-strike situations (though even in these situations, Kershaw’s most frequently used pitch is his fastball).

The emergence of the slider is particularly good given that Kershaw’s curveball, which looked so good when he first came up, has greatly decreased in value. When Kershaw broke into the majors in 2008, the curveball got an okay swinging strike rate of 9.9 percent and an amazing 70.6 percent GB rate, though that was only on 34 balls put into play.

In 2009, the swinging strike rate dropped a tiny bit to right-handed batters to 8.4 percent, but the GB rate dropped off a cliff to 38.5 percent, though this was on a small sample size of 39 balls in play.

In 2010, the drop-off in efficiency was seen in the swinging strike rate, plummeting to 6.6 percent as batters simply didn’t swing at the pitch as frequently as they had before. The GB rate recovered somewhat, though the sample size this year was even smaller (16 balls in play). As it is, this drop in effectiveness is not particularly worrisome due to the fact that the curveball’s use has decreased greatly in favor of the slider.

It should be noted that the slider was used more and more frequently compared to the curve in three of the last four months of the 2010 season. Thus, in April and spring training, we should keep an eye on what breaking ball Kershaw is using most frequently.

A good sign toward the future: Kershaw’s extreme accuracy at hitting the strike zone.

One thing that needs to be noted about Kershaw is this: he became much better at hitting the strike zone in 2010. In fact, using one measure of the strike zone (a wide zone, minimum 1500 pitches thrown), he hit the strike zone with his pitches at the 10th-best rate in all of the majors. According to another measurement of the strike zone (one that measures a smaller zone, minimum 1500 pitches thrown), he was the 13th best.

Now, Kershaw’s walk rate did improve from 2009 to 2010 a good bit, but still, his walk rate was actually 79th in the league out of 92 qualifying pitchers! How does that make sense?

Well it does make some sense: in reality, walk rate doesn’t correlate very strongly with a pitcher’s strike-zone rate (after all, pitchers do throw out of the zone on purpose on 0-2 and other counts where the odds of it causing a walk are extremely low). That said, there is some correlation (higher strike-zone rate, lower BB rate), and Kershaw actually has the highest walk rate of any pitcher with a strike-zone rate equivalent to, or higher than, his own rate.

This suggests that we would expect Kershaw, if he can keep up his improved accuracy, to improve his BB rate further. This makes sense of course: the strike-zone rate shows that Kershaw hit the strike zone at a very impressive rate, making it likely that he will use this ability to improve his walk rate in the future (as opposed to some pitchers that have an inability to hit the strike zone and, thus, are unlikely to lower their walk rate).


Clayton Kershaw is a REALLY good pitcher and is likely to continue to be such a good pitcher in the coming season. A PitchF/X analysis shows only one possible red flag: his fastball velocity has decreased each year. But the same analysis reveals more factors—the emergence of a strong breaking pitch in the slider and his improved accuracy—that show he could take another step toward being one of the best pitchers in the league.

For fantasy purposes, I’d consider Kershaw highly and would be willing to count on him for everything but wins (for obvious reasons). So though he might not get the press as some of the other amazing pitchers on bad teams, I’d consider him a guy who could potentially be in the same category by next year. There’s real potential there, which he looks really close to realizing. And even if he doesn’t, he’s already a great pitcher.

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  1. Jeff Jaffee said...

    Great analysis on Kershaw, who is a real pleasure to watch in person on a regular basis. I think one of the reasons for the slight drop in fastball velocity may be more concentration on the strike zone because of relatively high walk rate and pitch counts.  Kershaw’s only real weakness is not pitching as deep into games as the Dodgers would like, because of his high pitch count, although he’s improved greatly as he’s gained experience.  I was also surprised by the increasing numbers on his slider, because Clayton’s curve ball is killer.

  2. Lane Rizzardini said...

    I agree with Jeff. I read another analysis of Kershaw and they attributed the decrease in fastball velocity to, as Jeff said, a concentration on hitting the strike zone and working on the walk rate, which has clearly gone well. Considering his age, you could say he’s “maturing” as a pitcher.

    Now imagine he puts the speed and control together. Scary. I have him slated as a top-10 pitcher this year and going in the 5th round of most drafts, which is disappointing because I know I won’t get him then.

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