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Kenley Jansen is both better and worse than ever

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Jansen has added velocity and spin at the expense of knowing where the hell the ball is going.

MLB: MAY 28 Giants at Dodgers
I’m seeing double! There’s eight Kenley Jansens!
Photo by John McCoy/Icon Sportswire via Getty Images

Until the Giants tagged him for three runs in Friday night’s extra innings contest, Kenley Jansen hadn’t given up a run in the month of May. After appearing mortal for the past three years, Jansen has, at times, looked like the demigod for the first eight years of his career. He turned heads with this 95 mph cutter to Kyle Lewis that broke over a foot.

The witch-like horizontal movement isn’t the only remarkable thing about that pitch either. That pitch clocked in at 95 mph, and this is coming after a season in which Jansen’s cutter only averaged 90.9 mph. Indeed, Jansen’s maximum velocity on the cutter is 1.15 mph faster in 2021 than it was in 2020, and he’s been able to throw the sinker and slider harder than he’s been able since 2018.

Brooks Baseball

Not only is Jansen throwing harder, but he’s also imparting more spin than he ever has in his career. The average spin rate on his cutter is up to 2,814 from 2,553 the year before. He’s maxed out at 3,158 rpm which puts him into truly elite company.

Baseball Savant

From 2020 to 2021, Jansen has been one of the biggest gainers in spin rate. The 261 rpm that he added to his cutter is the biggest average gain of any pitcher from last fall to this spring. That was enough to take him from 29th on the leaderboard to fourth where he only trails Corbin Burnes and teammates Walker Buehler and Trevor Bauer. Below are the biggest changes in year-to-year spin rate from 2020 to 2021.

Cutter Spin Rate

Player 2020 2021 Gain
Player 2020 2021 Gain
Jansen, Kenley 2553 2814 261
Gonzalez, Chi Chi 2431 2680 249
McCullers Jr., Lance 2350 2569 219
Anderson, Tyler 2415 2615 200
Ottavino, Adam 2648 2807 159
Mayers, Mike 2196 2352 156
Kikuchi, Yusei 2256 2403 147
Godley, Zack 2184 2328 144
Lucchesi, Joey 2106 2249 143
Smith, Drew 2672 2812 140

As you might have surmised from his career average spin rate chart, his sinker and slider also saw some of the biggest gains in baseball from last season.

Sinker Spin Rate

Player 2020 2021 Gain
Player 2020 2021 Gain
Houck, Tanner 2082 2518 436
Cisnero, José 2024 2313 289
Borucki, Ryan 2168 2447 279
Crowe, Wil 2066 2330 264
Finnegan, Kyle 1917 2137 220
Santana, Dennis 2364 2566 202
Jansen, Kenley 2224 2417 193
Ottavino, Adam 2222 2395 173
Fulmer, Michael 2041 2202 161
Coonrod, Sam 2075 2226 151

What’s interesting is that of the 10 pitchers to have the largest gains in sinker spin, only fellow Dodger Dennis Santana had a higher average spin rate in 2020. Adam Ottavino and Ryan Borucki were the only other two within 100 rpm of Jansen.

The improvements on the slider are less pronounced compared to the sinker or cutter but still within the 10-best in MLB.

Slider Spin Rate

Player 2020 2021 Gain
Player 2020 2021 Gain
Lyles, Jordan 2361 2683 322
Borucki, Ryan 2315 2620 305
Hartlieb, Geoff 2238 2529 291
Alexander, Scott 2232 2453 221
Gonzalez, Chi Chi 2397 2618 221
Williams, Taylor 2473 2681 208
Waddell, Brandon 2418 2625 207
Crick, Kyle 3130 3330 200
Jansen, Kenley 2334 2531 197
Poppen, Sean 2036 2231 195

I’m not going to speculate that Kenley Jansen is using some sort of foreign substance to increase his spin rate, but I will speculate that MLB will investigate or has already begun investigating baseballs used in his outings. MLB is using spin rate data to identify pitchers who might be doctoring the baseball, and Jansen’s jumps fall within the range expected of a pitcher using some sort of grip enhancer.

No matter where the extra spin is coming from, neither of Jansen’s improvements—higher velocity, more spin—have clearly made him a better pitcher. His 2.01 ERA is his lowest since 2017, but his 31.0 strikeout rate is the third-lowest of his career and his 18.4 walk rate is more than double his next-highest mark and ranks in the bottom two percent of the league.

Jansen is throwing a career-low 39.8 percent of balls in the strike zone. Hitters are swinging are only swinging 44.4 percent of the time, another career-low mark. When hitters do swing, they’re making less contact. His 35.5 percent whiff rate is his highest since 2017, but overall, his swinging strike rate of 14.8 is effectively the same as it was last year and nearly a point lower than it was the year before that. Jansen’s pitches have become harder to square up but easier to lay off of.

In terms of movement, the extra spin has had mixed results. On average, Jansen has added 0.8 inches of horizontal movement to his slider and his sinker regained 0.5 inches of movement. The cutter, meanwhile, has actually lost 1.2 inches of horizontal movement which seems counterintuitive given the GIF at the top. Even without that 1.2 inches, Jansen’s cutter still has the fourth-most break of any cutter in MLB.

Baseball Savant

The extra spin isn’t making Jansen’s cutter cut more, but it is making it drop less. In terms of vertical movement, the cutter has six inches more rise than it did last year. This has gotten him back to near-2017 levels when his cutter was worth -2.3 runs per 100 pitches and induced a 34.9 percent whiff rate. In 2021, the cutters has been worth -2.8 runs and induced a 34 percent whiff rate.

Baseball Savant

Yet with more rise, Jansen is also throwing his cutter lower in the zone. His average cutter is crossing the plate 2.65 feet above the ground. Across 2019 and 2020, it averaged 2.93 feet. Below is heat map showing the locations for his cutters in 2021.

Baseball Savant

Notice that he’s well below the zone, outside to the glove side as well as above the zone. Here are the locations of his cutters from 2019 to 2020.

Baseball Savant

That’s a much more centralized area which indicates that Jansen doesn’t have the same kind of command with the cutter as he has in previous years. I know that’s not the most revelatory statement that can be made about a guy with an 18.4 percent walk rate, but that it’s his primary fastball and not solely a breaking ball driving up the free passes is worth pointing out.

By runs allowed, velocity, and the eyeball test, Jansen has looked as dominant as he ever had, but the walks and general lack of command, he’s looked worse than ever. So far, it has all kind of averaged out to be a repeat of the last couple years. That wouldn’t be the worst thing. Mortal Kenley Jansen is still better than most pitchers, but Mortal Kenley Jansen is a bit underwhelming if only because we know he’s capable of so much more.


Kenny Kelly is the managing editor of Beyond the Box Score.