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.