Updated Potential Hitter K% Regressors — Jul 13, 2021

Last week, I quickly introduced my updated hitter xK% equation thanks to commenter suggestions. Let’s now put the new equation into action and update my potential hitter K% regressor list. The original list used the earlier version of this equation and can be found here. As you might have expected, many of the same names made this new list. The xK% equation is updated, but the result isn’t dramatically different than it had been. So I won’t be discussing the names I did last week, just the new ones.

Potential K% Regressors
Name L/Str/Pit% S/Str/Pit% F/Str/Pit% I/Str/Pit% 3-0c/PA% Pit/PA HBP/Pit% K% xK% Diff
Tony Kemp 19.4% 6.9% 17.1% 16.7% 4.4% 3.98 0.4% 16.4% 20.6% -4.3%
Starling Marte 15.2% 12.2% 19.4% 16.0% 2.2% 3.97 0.7% 21.2% 25.2% -4.0%
Carlos Santana 15.0% 10.2% 16.0% 16.7% 6.5% 4.13 0.2% 15.1% 18.4% -3.4%
Jose Abreu 17.4% 14.4% 17.6% 16.2% 2.0% 3.99 0.6% 23.9% 27.2% -3.3%
Wilmer Flores 18.5% 7.1% 18.4% 19.5% 3.7% 3.94 0.1% 12.2% 15.5% -3.3%
Yandy Diaz 18.5% 7.5% 15.0% 17.4% 7.5% 3.90 0.2% 15.8% 19.0% -3.3%
Josh Donaldson 13.4% 12.9% 17.2% 17.0% 4.1% 3.93 0.1% 19.9% 23.0% -3.2%
J.D. Martinez 11.4% 15.6% 19.9% 17.5% 2.8% 3.84 0.1% 22.5% 25.6% -3.1%
Jose Altuve 19.3% 8.3% 16.8% 19.8% 5.3% 3.65 0.2% 15.8% 18.9% -3.1%
Vladimir Guerrero Jr. 14.2% 12.9% 13.9% 18.0% 4.9% 3.77 0.3% 18.1% 21.1% -3.0%
League Average 16.7% 12.5% 17.7% 16.9% 4.4% 3.92 0.3%

Three of the top four names on this list made up the top three on last week’s last. However, the rest of the names changed, and now Jose Abreu is outperforming his xK% by a lesser margin thanks to the addition of HBP/Pit%, a mark he has doubled the league average rate in.

Despite posting the highest S/Str/Pit% mark since at least 2014 (as far as my data goes back), Carlos Santana has improved his K% versus the last two seasons. With a consistently low BABIP, his value is tied to that strikeout rate as he needs a strong one to ensure his batting average doesn’t kill you and that he has a chance at 30 homers given his mediocre HR/FB rate. At age 35, you never know when or if that age-related decline cliff is imminent.

Wilmer Flores has made exceptional contact once again this year and he has even upped his walk rate into double digits for the first time. But he’s posted a higher rate of looking and foul strikes, so xK% doesn’t think his strikeout rate should be as strong as it is. There would normally be significant batting average upside here, but Flores has typically suffered from a well below average BABIP and that hasn’t changed this year. His skill set, sans walk rate, isn’t too different from Santana’s in that he needs the low strikeout rate to maintain a reasonable batting average and make the most of his mediocre HR/FB rate.

Yandy Diaz has gotten his FB% back up near his breakout 2019 mark, but his HR/FB rate has crashed back into single digits. Without the power or batting average right now, he’s strictly an OBP league asset. However, he may be overperforming his strikeout rate, despite an elite S/Str/Pit%, and he needs to continue putting the ball in play to hold onto any fantasy value, especially in non-OBP leagues.

Josh Donaldson has improved his strikeout rate to the best mark since 2016, but xK% isn’t buying it. While his HR/FB rate has slipped, his FB% has jumped to its highest mark since 2017, offsetting the loss of home run power with more balls in the air. But with all his other power-related Statcast metrics looking good, there’s really nothing here that suggested any sort of age-related decline.

This xK% is actually right in line with his historical actual strikeout rates once intentional walk plate appearances are excluded. But it does suggest that he’s been a bit fortunate at the moment. Martinez posted a 27.3% HR/FB rate in April, making us believe that last year was the fluke and the elite power version of himself is back. Unfortunately, he has posted low double digit marks since then, so now you have to wonder if April was the hot streak that actually won’t be repeated.

After a brutal 2020, Jose Altuve is back. But if xK% were to be believed, perhaps not as back as his results suggest. Last year his strikeout rate hit a career high and although this year he has improved it, it’s possible he should currently be sitting at another career worst. His strikeout rate didn’t used to be as important when he was posting BABIP marks well above .300, but now for a second year in a row with a mark below .300, suddenly his strikeout rate does matter in his quest to get his batting average back above .300.

Finally, Vladimir Guerrero Jr. is having the massive breakout season everyone was hoping would occur first in 2019, then in 2020. He has posted a S/Str/Pit% just a bit higher than the league average, but that’s offset somewhat by lower marks in the other strike types. While I can’t imagine any of his owners are even thinking about trading him away, do acknowledge that a .344 BABIP is tough to sustain, especially with a rather league averageish batted ball type distribution profile, plus a HR/FB rate over 30% is even more difficult, especially as that is nearly double his 2020 mark.

Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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slappy jack
10 months ago

JDM HR/FB is back at 20% in July; not sure what HR/FB has to do with K% regression anyway

10 months ago
Reply to  Mike Podhorzer

So if JDM goes from a 22.5 % to 25.6% strikeout rate over the course of the remainder of the season, in his remaining 250 or so at-bats, JDM will have an additional 8 Ks (3.1% of 250) = 8 fewer balls in play = 3 less fly balls (at JDM’s FB% rate of, say, about 37.5%) = somewhere just north of 1/2 a HR (at JDM’s HR/FB rate). Or about half the number of grand slam HRs that Daniel Camarena has in 2 career plate appearances.

Is it really worth all the math effort to discover that? Aren’t we just talking about noise here? I just do not see any of this data being actionable for fantasy purposes.

10 months ago
Reply to  LenFuego

When you lose your league by half a home run, you’ll wish you did the math!

10 months ago
Reply to  stonepie

With Acuna, Bauer, Mondesi, Bieber and Moustakas on my team, the fantasy gods seem to be taking care of that themselves and making that half a home run pretty moot :0*(