In "A Confession," his autobiographical account of a crisis of depression and estrangement from the world, Leo Tolstoy wrote the following passage:
I said to myself, ‘Everything develops, differentiates, moving towards complexity and refinement and there are laws governing this progess.'
The time came when I stopped growing; I felt that I was no longer developing but was drying up, my muscles were growing weaker, my teeth falling out, and I saw that this law not only failed to explain anything to me but that there had never been and never could be such a law… and it became clear to me that there could be no law of perpetual development.
Such may have been the case for Tolstoy, but it seemingly isn’t true for Dodgers closer Kenley Jansen. He’s continued to get better each year, and he will presumably continue to get better each year, until he is banned from baseball for being too challenging for opposing batters to face.
Now, let’s look at a table that proves the first part of that last sentence. Do keep in mind, of course, that he’s only thrown 23.2 innings to date, which isn’t very many innings at all, but there are some interesting insights we can glean.
If we just remove 2015 and its small, small sample altogether, we can see that Jansen’s FIP and xFIP, along with his FIP- and xFIP-, have improved each of the last few seasons. From 2012 to 2014, his strikeout and walk rates changed a bit each season, but it’s not like Jansen took a huge leap backward or forward in any of those seasons. He still struck out a staggeringly high amount of batters and walked batters at a league-average or better rate.
Looking at 2015, we can think of this as the most extreme version of Kenley Jansen. Among relievers with at least 20 innings pitched, Jansen’s FIP currently ranks as fourth-best in the majors, and he has posted the second-best xFIP. His strikeout rate would be the fourth-best single-season K percentage since 1900 if the season ended today ---- he’d only be trailing 2014 Aroldis Chapman, 2012 Craig Kimbrel, and this year’s edition of Carter Capps.
He’s getting strikeouts and limiting walks by pitching in the zone, throwing first pitch strikes, and getting more whiffs than ever:
Jansen is getting batters to swing at his pitches more often and getting them to miss with those swings more often, all while throwing in the zone more than he had previously. At this point, you’re probably wondering how he’s making all of those things happen (a GREAT question!).
One of the bigger differences is Jansen’s usage of his slider, as shown in the above graphic. Through 2010 and 2011, his first two years in the Dodger's bullpen, Jansen threw his slider a little more often than he does today, posting usage rates of about 10 and 12 percent, respectively. He cut that usage in half, however, from 2012 to 2014.
This adjustment didn’t really affect Jansen in terms of being a good pitcher --- he’s been a good pitcher since he came up, but this year, with his slider usage right around 10 percent again, he’s having a career year. What is interesting is the 35 sliders he’s thrown this year aren’t the reason for the increase in strikeouts.
What's seen above is Jansen's use of the slider in two-strike counts. He's thrown a handful of them in those situations, and only three have resulted in strikeouts. A good many of the whiffs we’ve seen from Jansen have come on his cutter, which has been even more unhittable this year than in previous years.
Using the tools at Brooks Baseball, we can isolate Jansen’s cutter and see how he is deploying it. The pitch seemingly hasn’t improved in any way: it’s not moving any more or less either vertically or horizontally, and the velocity is actually down a tick compared to last year.
What has changed is Jansen’s location, which is up in the zone more often, to both right- and left-handed batters in two-strike counts. Again, keep in mind that he’s only thrown 23.2 innings, and that doesn’t give us much of a sample to work with. but that slight change might be helping him foster better results. Below is a gif of his cutter usage with two strikes.
One of the images is through 2014, and the other is for this year. Admittedly, there isn't a huge difference that really sticks out, but bear in mind that what we're seeing below is nearly the only difference in 2014 Kenley Jansen and this year's Kenley Jansen.
Kenley Jansen has been a good pitcher since the Dodgers called him up to the big leagues. Now that he’s added a slider and is pounding the zone like never has before, he has improved in a number of areas. Many players might credit their improvements to making small adjustments — maybe they change one small thing, and that small thing makes something click, but Kenley Jansen is showing us another way to improve: do everything better than you’ve ever done it before and throw your cutter up in the zone.
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Murphy Powell is a contributor at Beyond the Box Score. You can follow him on Twitter at @murphypowell.