Javier Baez and Swinging Strike Rate
Javier Baez has been getting quite a bit of acclaim since returning to the Cubs with his reduced strikeout rate. In 2014, Baez had a 42% strikeout rate (K%) in the majors and 2015 value of 22% K% looks to be a huge improvement. Don’t get too excited about this small sample of data as his swing strike rate (SwStr%) points to a strikeout rate which will likely increase quickly.
Historically, a hitter’s strikeout rate correlates almost identically to their swinging strike rate. The reason to use SwStr% instead of K% is because it stabilizes a bit faster. I took all hitters since 2002 who had at least 200 plate appearances in a season and found the linear correlation between their strikeout rate and swinging strike rate. The R-squared between the two values was .947 with the equation working out to:
K% = 2.25 * SwStr%
With this little bit of information, here is a look at Baez’s stats in the majors the past two seasons.
Season: SwStr%, Predicted K%, Actual K%
2014: 19.2%, 43.2%, 41.5%
2015: 18.5%, 41.6%, 22.2%
Baez’s crazy high 2014 strikeout rate is almost exactly in line with the strikeout rate projected using his swing strike rate. His 2015 strikeout rate is almost equal to his SwStr%.
Besides just looking at the predictive nature of SwStr% and K%, how have hitters with near 20% SwStr% done? Since 2002, only 19 hitters have reached the 100 PA plateau with a SwStr% between 18% and 18% which shows how little patience teams have with extreme strikeout hitters.
| NAME | Position | Season | SwStr% | K% | PA |
| Mike Zunino | C | 2014 | 18.2% | 36.1% | 476 |
| Miguel Olivo | C | 2007 | 18.2% | 27.2% | 469 |
| Russell Branyan | 1B/3B | 2002 | 18.9% | 39.9% | 435 |
| Miguel Olivo | C | 2010 | 18.1% | 29.7% | 427 |
| George Springer | OF | 2014 | 18.6% | 38.6% | 345 |
| Eliezer Alfonzo | C | 2006 | 18.2% | 25.9% | 309 |
| Carlos Pena | 1B | 2005 | 18.7% | 36.5% | 295 |
| Josh Phelps | DH | 2002 | 18.5% | 30.9% | 287 |
| Tony Clark | 1B | 2004 | 18.1% | 36.4% | 283 |
| Kelly Shoppach | C | 2011 | 18.2% | 35.7% | 253 |
| Russell Branyan | 1B/3B | 2005 | 19.0% | 39.6% | 242 |
| Dallas McPherson | 3B | 2005 | 18.6% | 31.2% | 220 |
| Jake Fox | OF | 2010 | 18.5% | 24.7% | 211 |
| Todd Greene | C | 2004 | 18.0% | 19.5% | 209 |
| David Ross | C | 2004 | 18.5% | 37.6% | 190 |
| Avisail Garcia | OF | 2014 | 18.2% | 25.6% | 190 |
| Bucky Jacobsen | 1B/DH | 2004 | 18.4% | 29.4% | 176 |
| Sal Fasano | C | 2005 | 18.8% | 25.6% | 174 |
| Russell Branyan | 1B/3B | 2011 | 18.5% | 32.3% | 146 |
The list of hitters basically contains catchers or hitters who struggled to stay in the league. Their average K% was 32% and the median value was 31%. Truthfully, I think a K% around 30% would be great for Baez, but if it creeps up into the 35% range, he will likely be less of a fantasy option.
Another rookie with similar contact issues is Joey Gallo. His SwStr% is currently at 22.3% which would project to a 50.1% K%. This season he has 46% K% so far, so his high K% seems legit. Both Gallo and Baez could provide a fantasy team with some good home run numbers, but they will be a huge drain on their team’s batting average.
Don’t buy any of the hype that Baez has turned a corner and is no longer striking out as much. He is missing pitches nearly as much as he did last season and I fully expect his K% to quickly get above 30%. Baez’s owners should look to sell while his value is higher to some other owner who believes in his lower strikeout rate.
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 four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR twice, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.
Avid Cubs fan here. The biggest difference for Baez this year is his 2 strike approach. The Cubs have tried to make Baez’ two strike approach similar to Rizzos where there is no leg kick or pre swing movement. I believe that’s the biggest difference in the change in K%. Also, his AAA numbers are significantly better than last year with this approach. How does the above analysis look when you only look at 2 strike SwSt%?
I was thinking the same thing as I read the article .If a hitter drastically changes his approach with 2 strikes on him ,it should be possible to strike out at a considerably lower rate than his SwST% would suggest that he would have
While Jeff extols the predictive value of the swinging strike rate, I notice a large variety of outcomes in the list, from 19.5% to 39.6%.
I suspect the 2-strike approach is the reason for the disparity. If I were conducting this analysis, I would have investigated that before presenting my findings. Unless I just really was sure that Baez stunk, then I would just throw it up there.
I believe his minor league performance is very predictive, and so far, it seems to be.
Russell Branyan was so great to root for. So much imaginary potential.
If you are a big swing and miss guy, a good way to cut down on your strikeouts is to swing at more of the strikes, and take more of the balls. And that’s exactly what Baez has done so far in 2015. And the relationship between his ZSwing% and his OSwing% looks much more normal in 2015 than in 2014. These facts point towards his 2015 improvement as being likely real.
Are you saying cub fans should remove the lipstick they put on their pig this year?
DONT YOU DARE REGRESS UNTIL FATNASTY PLAYOFFS ARE OVER
I’m not trying to be a jerk when I say that I simply don’t believe this: “The R-squared between the two values was .947 ”
I’ve looked into plate discipline a fair amount and I’ve never seen any per PA stat correlate that highly with any plate discipline stat. R values (not R-squared ones) greater than .5 are really hard to find. (I think swing rate and walk rate anti-correlate that well.) Given that swing strikes are correlated with swing and swinging is correlated with not striking out, I’d be shocked if this particular correlation is so strong.
You can count me among the commenters who believe there is some legitimate improvement here. Running his plate discipline stats through my K/BB estimator spits out an expected 26.9% K rate this year. That would be a tremendous improvement, but I don’t believe in it myself. The reason is that 59% of his contacted balls this year have been in play, with only 41% foul. He will not sustain this rate. The only guys who approach 60% in that stat are Ben Revere type players. Regressing him to league average (50% in play, 50% foul) would give him a 31.8% K rate, still a substantial improvement. Finally, regressing him to his last year’s numbers (46% in play, 54% foul) would result in a 34.2% K rate. So I would guess he will fall somewhere in the 30-35% range when all is said and done.
Knock out the catchers and you have 9 players who logged the requisite PAs. And of those only Tony Clark and possibly Springer have had careers. And Clark’s year was pretty much an abberation. He was really a 14% SwStr guy… So, I am not holding out hope.
Where in the linked article does it say that SwStr% stabilizes faster than K%? The whole premise of this article rests on that assumption, but I can’t find it anywhere.
Why don’t you post Kris Bryant’s numbers for comparison. I would love to see where Kris falls in line on a list like this because he swings and misses a ton, yet also works counts and takes walks. (which would tend to dispel any prediction just from sw/strk%)
I don’t know what Bryant’s sw/strk% is, but it seems like he swings at a ton of pitches and comes up empty, even with two strikes. His Strikeout percentage is 36% and I don’t see a lot of people doubting his ability or his future. I also don’t see much of a difference in approach/swing with 2 strikes, something which seems a bit different with Baez (at times! sometimes he’s still taking a hack) this year.
Not saying Bryant and Baez are the same animal, because that’s definitely not true with Bryant’s discipline and ability to walk, however for the purposes of this exercise with sw/strk%, it does seem appropriate to counter with another guy who has succeeded with a high swing and miss %.
I was actually able to find my own answer. For those interested, here are two other Cubs players and their respective sw/strik%:
Rizzo- 7.9%
Bryant- 16.7%
sw/strk% DOESN’T MEAN EVERYTHING.
Normally love Jeff’s stuff, but this article is just bizarre.
For one: “The reason to use SwStr% instead of K% is because it stabilizes a bit faster.” There is nothing in either of the linked articles supporting this. None. K% stabilizes after 60 PA’s, and if you’re to believe the changes he’s made to his approach are here to stay, it isn’t ridiculous to judge him based on his numbers this season alone. Just compare a few PA’s on video between this year and last year, he looks like a different hitter.
Also, no mention of contact rate? He improved his contact rate 7% and his o-contact 14% in the minors from 2014 to 2015. Both of these improvements have continued in to the majors at close to the same percentages.
Does this mean he’s not gonna fall apart due to K’s? Of course not. But man, there’s sure a lot more to this puzzle than just SwStr% (which incidentally is down to 16.7% as of today, but obviously well after this article).