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Craig Kimbrel should not be the Cubs closer

Opposing batters are no longer swinging at his curveball

Craig Kimbrel reacts to a Colin Moran home run on July 31
Photo by Nuccio DiNuzzo/Getty Images

As many of you know, my second favorite team is the Boston Red Sox. I was lucky enough to see them play a lot of baseball when I lived in Boston from 2007-14, which was basically a golden age of Red Sox baseball. I kept watching after I moved to Chicago and as a result, I’ve watched a lot of Craig Kimbrel over the years. When he is right he is one of the most devastating relievers in the game and many people believe he’s already put together a Hall of Fame-worthy resume. The thing is, he is not right at the moment and until he is he should no longer enter Cubs games in save situations.

In his career Craig Kimbrel has been a strikeout machine. His career K/9 is 14.58. He has struck out 899 batters across 555 innings. His career BB/9 is 3.58, which isn’t outstanding, but it’s never been a huge issue given the strikeout numbers. Over the course of his career he’s also very effectively limited the long ball with a HR/9 rate of 0.75 and a HR/FB rate of 11.3 percent.

Kimbrel has built this impressive record mainly on two pitches. He has a fourseam fastball that averages around 96 miles per hour. He combines that pitch with a knuckle-curveball that averages 85.5 miles per hour. Over his career both pitches have generated a ton of swing and miss due to their movement. In fact, this is his intro for Brooks Baseball Pitchf/x tool (emphasis mine):

Craig Kimbrel has thrown 9,996 pitches that have been tracked by the PITCHf/x system between 2009 and 2020, including pitches thrown in the MLB Regular Season, the MLB Postseason, The World Baseball Classic, Spring Training and Fall/Winter Ball. In 2020, he has relied primarily on his Fourseam Fastball (96mph) and Curve using a Knuckle Curve grip (86mph).

His fourseam fastball generates a high number of swings & misses compared to other pitchers’ fourseamers, generates a very high amount of groundballs compared to other pitchers’ fourseamers, has some natural sinking action, has well above average velo and has slight armside run. His curve is thrown extremely hard, generates an extremely high number of swings & misses compared to other pitchers’ curves, results in more flyballs compared to other pitchers’ curves and has slight glove-side movement.

I can sum up Craig Kimbrel’s current problems in Chicago in one table:

Craig Kimbrel select stats by season

Season IP K/9 BB/9 HR/9 HR/FB
Season IP K/9 BB/9 HR/9 HR/FB
2010 20.2 17.4 7.0 0.0 0.0%
2011 77.0 14.8 3.7 0.4 5.3%
2012 62.2 16.7 2.0 0.4 9.7%
2013 67.0 13.2 2.7 0.5 10.3%
2014 61.2 13.9 3.8 0.3 4.9%
2015 59.1 13.2 3.3 0.9 13.6%
2016 53.0 14.1 5.1 0.7 8.2%
2017 69.0 16.4 1.8 0.8 12.8%
2018 62.1 13.9 4.5 1.0 12.7%
2019 20.2 13.1 5.2 3.9 36.0%
2020 1.2 5.4 21.6 10.8 66.7%
Select stats Fangraphs

During his time in Chicago Kimbrel’s walk rate and HR rate have skyrocketed while the bottom has fallen out of his K-rate in 2020. I can already hear someone screaming “Small Sample Size” in the comments, so before you put me on blast for judging a future Hall of Famer on 1.2 innings I want to show you this stunning data from Statcast: Kimbrel has thrown 23 curveballs in 2020 and has not generated a swing and miss on ANY of them:

Craig Kimbrel Statcast by pitch type

Season # of Pitches MPH Spin Whiff %
Season # of Pitches MPH Spin Whiff %
2010 FB 276 96.1 33.0%
2010 Curve 83 85.2 50.0%
2011 FB 885 96.8 31.5%
2011 Curve 397 87.4 54.9%
2012 FB 604 97.5 38.3%
2012 Curve 300 86.3 50.8%
2013 FB 714 97.5 25.8%
2013 Curve 301 86.4 55.5%
2014 FB 760 97.7 31.4%
2014 Curve 287 85.9 53.8%
2015 FB 677 98.0 2453 30.3%
2015 Curve 288 87.3 2548 57.9%
2016 FB 642 98.0 2455 27.5%
2016 Curve 290 87.2 2555 56.5%
2017 FB 783 98.3 2428 39.3%
2017 Curve 360 87.3 2591 55.3%
2018 FB 718 97.1 2356 33.3%
2018 Curve 391 86.6 2579 55.6%
2019 FB 251 96.2 2323 24.8%
2019 Curve 126 85.9 2533 50.5%
2020 FB 34 96.4 2296 25.0%
2020 Curve 23 85.5 2476 0.0%
Select data Statcast

It isn’t just that batters aren’t swinging and missing on his curve. They aren’t swinging at the pitch at all. The closest thing that Kimbrel has generated to a swing on his curveball was this check swing from Franchy Cordero last night:

Franchy Cordero almost swings at a Kimbrel curveball
MLB | Marquee Sports Network

In 2020 Kimbrel has faced 15 batters with these results:

That is a big load of Y I K E S.

But there is more. Since batters clearly seem to be recognizing Kimbrel’s curveball they are able to just sit on his only other pitch — a fourseam fastball that has averaged right around 96.4 MPH in 2020. That pitch used to generate a lot of ground balls, now it generates a lot of hard contact, and, you guessed it — home runs. Here are the exit velocities on balls in play for Kimbrel in 2020:

Kimbrel exit velocity on balls in play 2020

Batter Result EV
Batter Result EV
Jesse Winker Groundout 74.7
Josh Bell Home Run 101.8
Colin Moran Home Run 102.6
Bryan Reynolds Groundout 104.7
Gregory Polanco Lineout 104.9
Cole Tucker Groundout 102.4
Salvador Pérez Single 105.1
Adalberto Mondesí Double 105.0
Batter, results and exit velocity Statcast

I do not think Kimbrel is irrevocably broken. The velocity is still there, but something mechanical is clearly off. I’m not sure whether he is tipping his pitches with his delivery or if the slightly larger gap in spin rate between his fourseamer and curveball are just making a big enough difference that players can recognize those pitches better now.

At the end of the day, it really doesn’t matter. It seems pretty clear that batters know what is coming from Kimbrel right now, and they are just mashing those fastballs. Until batters start offering at his curveball again it’s a huge gamble to put him in the game, let alone a save situation.