Jose Quintana’s K/9 and SwStr% Disconnect

Last week, I profiled Jose Quintana as a pitcher’s whose ADP and our auction value differed. In my analysis, I noticed that his swinging strike rate (SwStr%) and strikeout rate (K/9) didn’t move in tandem. Here are the pair plotted against each other.

And here are his historic values showing he doesn’t have a propensity to have a higher strikeout rate than his swinging strike rate suggests.

Comparison of Jose Quintana’s K/9 and SwStr%
Season K/9 SwStr%
2012 5.4 8.3%
2013 7.4 8.9%
2014 8.0 8.3%
2015 7.7 9.2%
2016 7.8 7.6%
2017 9.9 8.4%

Quintana’s projections seemed based off his strikeout jump, not his swing-and-miss numbers. Steamer has him pegged for a 9.1 K/9 for 2018. Today, I’m going to look to see if just looking at strikeouts rates and not swing-and-miss totals is the correct procedure moving forward.

First, I need to clear up one misconception, the jump in strikeout rate without a SwStr% boost was not from a change in leagues. His strikeouts did jump from 9.4 K/9 to 10.5 K/9 while his SwStr% stayed almost the same going from 8.4% to 8.6%. The AL-based 9.4 K/9 would be a career high for him so the difference existed before the trade.

To find out the normal transition, I compared all starters who moved from one league to another since 2002. In total, 55 moved from the AL to the NL and 48 from the NL to AL. Here’s how the numbers changed.

Effects on K/9 and SwStr% When Change League
League move Median K/9 Change Weighted K/9 Change Median SwStr% Change Weighted SwStr%
AL to NL 0.30 0.43 0.45% 0.43%
NL to AL -0.41 -0.28 -0.41% -0.16%

On average, the pitchers moving to the NL saw their K/9 go a quarter to a half run higher. The swinging strike rate made a similar change with nearly a quarter to half percentage point change.

Getting back to Quintana, both of his changes are in line with the historic changes with his K/9 changing a bit more and his Swtr% maybe a bit less.

Now that the move can be removed as a factor, here is a plot of the K/9 and SwStr% numbers since 2014 for pitchers with 120 IP. Originally, I meandered down a path with values back to 2002 and found the difference between K/9 and SwStr% changing over time. The reason was a changing strike zone as outlined by Jon Roegele at The Hardball Times. The 2017 strike zone was most similar to the zones from 2014 to 2016 so I used these seasons.

While the r-squared is not 1.0, a .65 value is a decent amount of correlation. Using the above equation, normally a pitcher with an 8.4% SwStr% would have a K/9 of 7.1, not a 9.9 K/9. There is a reason Quintana’s difference sticks out because of the 480 pitchers in the sample, his varied the most.

Largest Differences Between Estimated and Actual K/9
Name Season IP K/9 SwStr% Estimated K/9 Difference
Jose Quintana 2017 188.2 9.9 8.4% 7.1 2.8
Yu Darvish 2014 144.1 11.3 10.9% 8.6 2.7
Stephen Strasburg 2016 147.2 11.2 11.0% 8.7 2.5
Trevor Bauer 2017 176.1 10.0 9.2% 7.5 2.5
Nick Pivetta 2017 133.0 9.5 8.7% 7.2 2.3
Robbie Ray 2016 174.1 11.3 11.6% 9.0 2.2
Ubaldo Jimenez 2014 125.1 8.3 6.9% 6.1 2.2
Stephen Strasburg 2015 127.1 11.0 11.2% 8.8 2.2
Archie Bradley 2016 141.2 9.1 8.2% 6.9 2.2
Rich Hill 2017 135.2 11.0 11.5% 8.9 2.1

Now, which value, as more weight the next season? Here are the top-twenty pitchers who had the biggest change and still met the criteria of 120 IP and a starter (GS/G >= 0.5)?

How Pitchers With the Largest Differences Between Estimated and Actual K/9 Performed
Name Y1 IP SwStr% K/9 PK/9 diff Y2 IP SwStr% K/9 Y2 K/9 – Y1 K/9 Y2 pK/9 – Y1 K/9 Y2 SwStr% – Y1 SwStr%
Stephen Strasburg 2016 147.2 11.0% 11.2 8.7 2.5 2017 175.1 12.9% 10.5 -0.7 1.8 1.9%
Robbie Ray 2016 174.1 11.6% 11.3 9.0 2.2 2017 162.0 14.2% 12.1 0.9 3.1 2.6%
Ubaldo Jimenez 2014 125.1 6.9% 8.3 6.1 2.2 2015 184.0 8.0% 8.2 -0.1 2.1 1.1%
Stephen Strasburg 2015 127.1 11.2% 11.0 8.8 2.2 2016 147.2 11.0% 11.2 0.2 2.4 -0.2%
Hector Santiago 2014 127.1 6.9% 7.6 6.1 1.6 2015 180.2 8.5% 8.1 0.4 2.0 1.6%
Kyle Hendricks 2015 180.0 8.1% 8.4 6.8 1.5 2016 190.0 10.0% 8.1 -0.3 1.2 2.0%
Bartolo Colon 2014 202.1 5.6% 6.7 5.3 1.5 2015 194.2 6.4% 6.3 -0.4 1.0 0.8%
Jake Odorizzi 2014 168.0 9.7% 9.3 7.9 1.4 2015 169.1 10.1% 8.0 -1.3 0.1 0.4%
David Price 2014 248.1 10.6% 9.8 8.4 1.4 2015 220.1 11.9% 9.2 -0.6 0.8 1.3%
Ubaldo Jimenez 2015 184.0 8.0% 8.2 6.8 1.4 2016 142.1 8.3% 7.9 -0.3 1.1 0.3%
Jake Arrieta 2014 156.2 10.4% 9.6 8.3 1.3 2015 229.0 11.1% 9.3 -0.3 1.0 0.7%
C.J. Wilson 2014 175.2 7.4% 7.7 6.4 1.3 2015 132.0 8.6% 7.5 -0.2 1.1 1.2%
Andrew Cashner 2016 132.0 7.3% 7.6 6.4 1.3 2017 166.2 6.1% 4.6 -3.0 -1.7 -1.2%
Jose Quintana 2016 208.0 7.6% 7.8 6.6 1.3 2017 188.2 8.4% 9.9 2.0 3.3 0.8%
J.A. Happ 2014 158.0 7.2% 7.6 6.3 1.3 2015 172.0 8.1% 7.9 0.3 1.6 0.9%
Stephen Strasburg 2014 215.0 11.4% 10.1 8.9 1.2 2015 127.1 11.2% 11.0 0.8 2.1 -0.2%
Gerrit Cole 2014 138.0 9.6% 9.0 7.8 1.2 2015 208.0 10.2% 8.7 -0.3 1.0 0.6%
Ian Kennedy 2014 201.0 10.1% 9.3 8.1 1.2 2015 168.1 10.3% 9.3 0.0 1.2 0.3%
Andrew Cashner 2015 184.2 8.2% 8.0 6.9 1.1 2016 132.0 7.3% 7.6 -0.4 0.7 -0.9%
Max Scherzer 2014 220.1 11.8% 10.3 9.2 1.1 2015 228.2 15.3% 10.9 0.6 1.7 3.5%
Average 1.5 Average -0.1 1.4 0.9%
Median 1.4 Median -0.2 1.2 0.8%

The pitchers who have the biggest disconnect between their K/9 and SwStr% keep their disconnected K/9 numbers going into the next season. For those who just want the short simple answer, they should expect Quintana to continue with the high strikeout numbers.

One obvious change is that the pitchers’ SwStr% jumped the next season putting it more in-line with their K/9. The near 1%-point change does not account for all the 0.5 point change in K/9. The difference averages out to 1.5 K/9. Just some change is explained.

I have a theory on why the difference is even more.

According to Baseball Prospectus, all of the catchers that were behind the dish for Quintana were markedly better than what he got from his primary catcher in 2016, Dioner Navarro. Even his secondary catcher from ’16, Alex Avila, was holding him back compared to his 2017 crew, which again included Avila once Quintana was traded. Avila’s framing took a big step forward from Detroit to Chicago, though that’s probably due in large part to the quality of arms throwing. At any rate, Q got framing bumps that no doubt helped his strikeout rate.

Jose Quintana’s strikeout and swinging strike rate don’t seem to jive. Don’t worry about the difference. Of the pitchers with the most extreme disagreements, the strikeouts rate is more predictive going forward with most of the gains sticking. The reason behind the gains staying is a not exactly known but they do continue. With pitchers normally keeping their gains, owners can pick up Quintana and expect him to keep his 2017 strikeout gains.





Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won three FSWA Awards including on for his MASH series. In his first two seasons in Tout Wars, he's won the H2H league and mixed auction league. Follow him on Twitter @jeffwzimmerman.

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Mark Davidson
Member

The Castro and Quintana paragraph is a little confusing. What am I missing?
Good analysis, otherwise.

Mark Davidson
Member

Maybe Jason Castro helped increase the Twins’ staff’s K rate without influencing their SwStrk% – i believe that.
And maybe the way Quintana commands his pitches makes it easier for catchers to frame – I believe that.
But wouldn’t you want to split up that paragraph to show the how those two aspects affect K rate without affecting SwStrk%?
Or did Castro and Quintana play together at some point last year? I feel like I’m going crazy trying to remember that.

Magnus Olsson
Member

I’m pretty sure the writer has Twins confused with either White Sox or Cubs as only Castro played for the Twins last season.