Studying Strikeout Rates: Whose Will Rise & Whose Will Fall?

Masahiro Tanaka has carried the Yankee staff this season in a large part thanks to his league-leading Swinging Strike Rate.

Masahiro Tanaka has carried the Yankee staff this season thanks to his league-leading Swinging Strike Rate.

When looking at early season statistics, it’s important to see what can be sustained and what cannot. A third of the season is already in the books, and when it comes to projecting the final two thirds of the year only one thing is certain: some players will regress from unrealistic paces, and others will improve from slow starts to the season.

One way to see what pitchers have under or over-performed is in their strikeout rate. Theoretically, the correlation between the amount of swing-and-misses a pitcher gets and the amount of strikeouts they get should be nearly 1 –  however, strike outs looking, “clutch” swing-and-miss pitches on strike 3, and pure variance will lead to a much lower correlation. I took a look at this year’s 102 qualified pitchers and compared their K% rate and their SwStr% rate:

SwStr Graph

I created the “expected K%”, or xK%, for each pitcher by normalizing their swinging strike rate to the yellow line on the graph, which shows the best-fit line of the data for all 102 qualified pitchers. This is what in the long-run will be the average K rate of a pitcher with that given swinging strike rate. While some pitchers may be better at getting strikeouts looking or reaching back for a swing-and-miss on strike 3, this is where most pitchers should end up. The correlation so far this year is at .55, while last year at the end of the year the correlation was .72. This shows how pitchers over a larger sample will be closer and closer to the line.

This brings us to the final statistic, K%-xK%. This shows where a pitcher’s been “lucky” or “unlucky,” with high numbers pointing to pitchers that are performing over their heads, and negative numbers pointing to pitchers that should be striking out more batters the rest of the way. All of the data I compiled is in a sort-able table below:

NameTeamSwStr%K%xK%K%-xK%
Masahiro TanakaYankees14.30%28.70%28.91%-0.21%
Francisco LirianoPirates14.20%23.00%28.75%-5.75%
Tyson RossPadres12.60%22.20%26.10%-3.90%
Ervin SantanaBraves12.40%22.40%25.76%-3.36%
Stephen StrasburgNationals12.30%28.50%25.60%2.90%
Zack GreinkeDodgers12.20%28.30%25.43%2.87%
Felix HernandezMariners12.10%24.80%25.27%-0.47%
Corey KluberIndians11.90%28.40%24.94%3.46%
Michael WachaCardinals11.90%25.20%24.94%0.26%
Madison BumgarnerGiants11.80%27.50%24.77%2.73%
Max ScherzerTigers11.60%27.70%24.44%3.26%
Yordano VenturaRoyals11.40%24.30%24.11%0.19%
Edwin JacksonCubs11.20%22.30%23.78%-1.48%
Jason HammelCubs11.00%22.70%23.44%-0.74%
Dallas KeuchelAstros10.90%21.50%23.28%-1.78%
Julio TeheranBraves10.90%20.30%23.28%-2.98%
John LackeyRed Sox10.80%22.70%23.11%-0.41%
Jorge de la RosaRockies10.60%19.70%22.78%-3.08%
Alex WoodBraves10.50%25.00%22.61%2.39%
Jordan ZimmermannNationals10.50%19.40%22.61%-3.21%
R.A. DickeyBlue Jays10.40%18.90%22.45%-3.55%
Yu DarvishRangers10.20%29.50%22.12%7.38%
David PriceRays10.20%25.60%22.12%3.48%
Garrett RichardsAngels10.10%23.30%21.95%1.35%
Homer BaileyReds10.10%19.90%21.95%-2.05%
Aaron HarangBraves9.90%24.20%21.62%2.58%
Jon LesterRed Sox9.80%29.10%21.45%7.65%
Ian KennedyPadres9.80%27.00%21.45%5.55%
Hiroki KurodaYankees9.80%17.30%21.45%-4.15%
Marco EstradaBrewers9.70%22.80%21.29%1.51%
Scott KazmirAthletics9.70%19.90%21.29%-1.39%
Matt GarzaBrewers9.70%19.30%21.29%-1.99%
Tim HudsonGiants9.70%16.80%21.29%-4.49%
Josh BeckettDodgers9.50%23.60%20.96%2.64%
Tim LincecumGiants9.50%22.90%20.96%1.94%
Jason VargasRoyals9.50%18.50%20.96%-2.46%
Drew HutchisonBlue Jays9.40%21.70%20.79%0.91%
Jeff SamardzijaCubs9.40%21.00%20.79%0.21%
Justin MastersonIndians9.40%19.00%20.79%-1.79%
Johnny CuetoReds9.20%26.70%20.46%6.24%
James ShieldsRoyals9.20%20.70%20.46%0.24%
Justin VerlanderTigers9.20%16.50%20.46%-3.96%
Roenis EliasMariners9.10%21.30%20.29%1.01%
Adam WainwrightCardinals9.00%24.70%20.13%4.57%
Wade MileyDiamondbacks8.90%21.00%19.96%1.04%
Phil HughesTwins8.80%19.90%19.80%0.10%
Tom KoehlerMarlins8.80%15.90%19.80%-3.90%
Jesse ChavezAthletics8.70%22.70%19.63%3.07%
Kyle LohseBrewers8.70%19.70%19.63%0.07%
Zack WheelerMets8.60%22.70%19.47%3.23%
Miguel GonzalezOrioles8.60%19.80%19.47%0.33%
Gerrit ColePirates8.50%20.80%19.30%1.50%
Sonny GrayAthletics8.50%19.70%19.30%0.40%
Jered WeaverAngels8.50%18.00%19.30%-1.30%
Chris ArcherRays8.40%21.60%19.13%2.47%
Brandon McCarthyDiamondbacks8.40%20.50%19.13%1.37%
Lance LynnCardinals8.40%19.80%19.13%0.67%
Rick PorcelloTigers8.40%16.30%19.13%-2.83%
Juan NicasioRockies8.40%14.80%19.13%-4.33%
Wei-Yin ChenOrioles8.30%17.00%18.97%-1.97%
Ricky NolascoTwins8.30%14.70%18.97%-4.27%
Jake PeavyRed Sox8.20%17.60%18.80%-1.20%
John DanksWhite Sox8.20%16.60%18.80%-2.20%
Cliff LeePhillies8.10%21.10%18.64%2.46%
Wily PeraltaBrewers8.00%18.60%18.47%0.13%
Tyler SkaggsAngels8.00%18.30%18.47%-0.17%
Nathan EovaldiMarlins7.90%19.60%18.31%1.29%
Alfredo SimonReds7.90%15.10%18.31%-3.21%
Franklin MoralesRockies7.90%15.10%18.31%-3.21%
Jose QuintanaWhite Sox7.80%19.40%18.14%1.26%
C.J. WilsonAngels7.70%22.60%17.97%4.63%
Hyun-Jin RyuDodgers7.70%20.80%17.97%2.83%
Ryan VogelsongGiants7.70%19.40%17.97%1.43%
A.J. BurnettPhillies7.60%19.80%17.81%1.99%
Edinson VolquezPirates7.60%16.10%17.81%-1.71%
Chris TillmanOrioles7.40%17.50%17.48%0.02%
Josh CollmenterDiamondbacks7.40%15.50%17.48%-1.98%
Kyle KendrickPhillies7.40%14.00%17.48%-3.48%
Kyle GibsonTwins7.40%12.00%17.48%-5.48%
Shelby MillerCardinals7.30%17.20%17.31%-0.11%
Ubaldo JimenezOrioles7.20%21.60%17.14%4.46%
Tanner RoarkNationals7.20%17.80%17.14%0.66%
Mike LeakeReds7.20%16.20%17.14%-0.94%
Travis WoodCubs7.10%20.30%16.98%3.32%
Tommy MiloneAthletics7.00%15.20%16.81%-1.61%
Henderson AlvarezMarlins7.00%14.20%16.81%-2.61%
Andrew CashnerPadres6.90%19.30%16.65%2.65%
Dan HarenDodgers6.90%17.30%16.65%0.65%
Eric StultsPadres6.80%11.50%16.48%-4.98%
Charlie MortonPirates6.70%15.30%16.32%-1.02%
Jordan LylesRockies6.60%16.90%16.15%0.75%
Bud NorrisOrioles6.60%15.60%16.15%-0.55%
Bronson ArroyoDiamondbacks6.30%13.10%15.65%-2.55%
Jon NieseMets6.20%17.80%15.49%2.31%
Mark BuehrleBlue Jays6.00%13.90%15.16%-1.26%
Jeremy GuthrieRoyals6.00%11.80%15.16%-3.36%
Bartolo ColonMets5.90%18.70%14.99%3.71%
Jarred CosartAstros5.90%15.40%14.99%0.41%
Chris YoungMariners5.60%11.70%14.49%-2.79%
Yovani GallardoBrewers5.50%16.60%14.33%2.27%
Kevin CorreiaTwins4.50%12.50%12.67%-0.17%

Click the category atop each column to sort by that and click the arrows at the bottom right corner to go to the next page of data. 

As you can see, there is a wide spread of over and under achievers among elite and sub-par pitchers. The highest K%-xK%’s belonged to Jon Lester (7.65%), Yu Darvish (7.38%), and Johnny Cueto (6.24%). All three should remain effective pitchers, but expect their elite K rates to drop a little bit, and Lester in particular could be a good sell-high candidate.

On the other side of the spectrum, some of the pitchers who should see a rise in strikeouts include Francisco Liriano (-5.75%), Hiroki Kuroda (-4.15%), and Justin Verlander (-3.96%), which is great news for their fantasy owners and makes them a good target in a trade. Tyson Ross is another name that pops up on the list, due to his 12.60% Swinging Strike rate, good for 3rd in the league. He is undervalued right now in nearly every league, and is becoming one of my favorite young arms due to his ability to generate lots of strikeouts and ground balls.

This list should be a good way to study strikeout rates across the league and project the pitchers that will improve or decline the rest of the way, but is far from a definitive projection. Some pitchers will continue to show an ability to maintain their extreme rate (be it higher or lower than the average).

Matt Cott is a co-founder of RotoAnalysis. Follow him on Twitter @RotoAnalysis and @KidCotti21! 

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