Potential Hitter K% Regressors — Jul 7, 2021

Yesterday, I used my newly unmasked hitter xK% equation to identify and discuss the hitters who have most underperformed the metric. Today, let’s now look into the biggest overperformers, or hitters who may be deserving of a higher strikeout rate right now.

Potential K% Regressors
Player Pit/PA L/Str S/Str F/Str 30% K% xK%
Starling Marte 3.96 24.2% 18.9% 31.0% 2.9% 19.9% 24.8%
Jose Abreu 3.99 26.2% 22.4% 26.8% 2.1% 24.4% 28.5%
Tony Kemp 3.98 31.7% 11.7% 29.2% 4.3% 16.7% 20.5%
Jose Iglesias 3.72 23.6% 15.2% 31.3% 2.2% 15.6% 19.3%
Anthony Rizzo 3.84 26.5% 15.4% 29.2% 7.7% 15.8% 19.5%
Sean Murphy 3.64 27.6% 21.6% 24.5% 4.6% 25.1% 28.7%
Jonathan India 4.06 31.5% 19.4% 23.5% 6.2% 22.1% 25.4%
League Average 3.94 26.4% 19.6% 27.5% 4.7% 23.8%

Starling Marte easily heads the list of overperformers. But that shouldn’t be as serious cause for concern as it might for another hitter. Why? Because Marte has actually outperformed his xK% every single season of his career that I’ve calculated it for (going back to 2014). And it hasn’t even been minor differentials either — his outperformance has ranged from 1.0% to 3.4%, excluding this season. Yes, he has outperformed by the highest margin so far this year, which is definitely a concern, but given his history, I wouldn’t expect him to regress all the way up to his xK%. We know that a one-size-fits-all equation is never going to work on 100% of the player population, and Marte appears to be one of the outliers, consistently doing something not being accounted for here. The most exciting part of Marte’s season is his sudden willingness to take a walk, as his walk rate has more than doubled. For a stolen base guy, wll those extra times on base is huge.

Jose Abreu has also outperformed his xK% each season, but not to the degree that Marte has. Abreu has typically beaten his xK% by between 0.5% and 2.0%, so while it means he probably won’t revert all the way toward his xK%, his current gap is double his previous largest gap. It’s a bad sign either way, especially since his strikeout rate already represents a career worst, and the fourth straight increase. Predictably, Abreu has fully regressed back to his pre-2020 season after a career half year, as both his BABIP and HR/FB rate have dropped back toward career averages. At age 34, I wouldn’t expect a hot streak to put him back on a 2020 pace and the jump in strikeout rate is a potential red flag of a performance decline.

With a massive walk rate and some power, Tony Kemp has been a pleasant surprise for the Athletics, even if that still hasn’t translated into significant fantasy value, outside of OBP leagues. He swings and missed quite infrequently, but a patient approach has resulted in lots of looking strikes. Obviously, this is not the type of profile that could afford to strike out more than he has, even if an increased strikeout rate would still be better than the league average.

Jose Iglesias has been a consistent xK% beater as well, and amazingly, has never outperformed by less than 2.3%. His outperformance has actually ranged between that 2.3% and 3.8%, so he has been a consistently consistent beater. This season’s gap would represent a career high by a marginal degree. It’s still a worry though as his strikeout rate already sits at a career worst, driven by a spike in S/Str. For someone that very rarely takes a walk, he needs as many balls in play as possible to keep his OBP above .300.

I’m almost getting tired of typing this, but Anthony Rizzo is yet another consistent xK% beater, having done so by significant degrees in the past (as much as 4.6%). So this year’s 3.7% outperformance is actually right in line with his past. It’s interesting that his HR/FB rate is at its lowest mark since 2013, despite his highest HardHit%, EV, and Barrel%, and second highest maxEV. Those seeming mismatches might have something to do with his xwOBA sitting 26 points higher than his actual wOBA.

Sean Murphy is hitting just .225 already, and owns a strikeout rate that xK% suggests should be dramatically higher. That’s not a good sign for his batting average moving forward, unless he could improve upon the underling skills driving that xK% mark. The good news is he continues to display ample power and his xwOBA suggests his batted ball quality has actually been better than last year when he posted a 22.6% HR/FB rate.

I have to admit, I was not expecting Jonathan India to perform so solidly, be a strong fantasy contributor, or even remain in the Majors through the end of May after he skipped Triple-A and only recorded 145 plate appearances at Double-A. But right now, the skill set has been quite respectable, with contributions all around. That said, xK% suggests he is deserving of a slightly worse strikeout rate. More strikeouts could cut into his stolen base opportunities and runs scored potential.

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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Joe Wilkeymember
2 years ago

You knew I was going to comment. 😉

My xK% has Iglesias as an almost exact match for his actual. The driving factor behind that is his ability to put the ball in play. Looking at Baseball Reference, Iglesias has seen 1043 pitches this year, and he’s put roughly 224 of them in play, which is 21.5% of all pitches. League average is 16.8%. If you assume he has an equal chance of putting every pitch in play (a bad assumption, I know, but just go with me), the odds of him not putting a ball in play in the first three pitches of a PA are .785^3 = 48.4%. A league average hitter has a .832^3 = 57.6% chance of the same thing. I guess your equation implicitly takes this into account, but since Iglesias swings a lot and puts the ball in play a lot, he’s always going to be an outlier in your system.

I do have to ask one thing: would this be a better system if the denominator on the variables was total pitches instead of strikes? I would think the volume of strikes would be an important factor in an xK equation.

Joe Wilkeymember
2 years ago
Reply to  Mike Podhorzer

Definitely agree with that last statement. Trevor Bauer has vexed my systems every year.