Image credit: Vincent Carchietta-USA TODAY Sports
Translated by Fernando Battaglini
I subscribe to SiriusXM. The reason is that I spend more time than I would like driving during the summer and you can listen to the local broadcast of all the baseball games on SiriusXM. I listened to the entirety of Roy Halladay’s Perfect Game during a long drive. For me it is worth the money.
During the off season, I can’t listen to the games. However, I still tune in to two shows. One is “Behind the Numbers,” a weekly show hosted by Vince Gennaro. He and his guests talk about a variety of topics, usually geared toward baseball analytics. The other is “Power Alley,” hosted by Mike Ferrin and Jim Duquette. They also do interviews, but mainly the two discuss current baseball events for three hours, Monday through Friday. I even have an “All Access” subscription so I can listen to them at my own time, when I’m not in the car.
Ok, end of SiriusXM commercial. The reason I told you about this is that on May 2, during a long trip, I was listening to Duquette and Ferrin. They were talking about the Braves who, at the time, were in first place and about to start a weekend series in Los Angeles against the Dodgers. They noted that Ronald Acuña Jr., with just one home run and a .322 slugging percentage, was well behind his 2023 MVP pace. One factor was strikeouts. Acuña had struck out in 23.6% of his plate appearances in 2021-22, but reduced that rate to 11.4% last season. However, up to that point this year, he had struck out in 27.9% of his plate appearances.
Ferrin commented: “One article I would read, in case someone writes for a data-driven site and wants to write about this: the connections between extreme strikeout rates and how they change from year to year.”
Thanks not only for the article idea but also for the title, Mike!
I looked at all hitters from 1998 to 2023 (the 30-team era), limiting the sample to players with at least 200 plate appearances. That yielded 8,863 playing seasons. I then looked for cases of players whose strikeout percentage fell or increased by at least 5% in consecutive seasons with at least 200 plate appearances.
There were 289 players whose strikeout rate fell by at least 5% in consecutive years. The average drop was 6.7%. The biggest drop was recorded by Matt Olson: 31.4% in 2020 and 16.8% in 2021. Acuña’s 12.2% drop from 2022 to 2023 would rank fifth. But it’s not like that; I considered only players who had at least one season with more than 200 plate appearances afterwards, so I could see if they maintained their improvement.
The answer is: on average, they did. At least in part. The average player whose strikeout rate fell 5% or more regressed, in part, in subsequent years. His strikeout was 4.3% lower than before the next season, 4.2% the season after that, and 3.2% three years later. So, on average, these hitters were able to retain nearly two-thirds of the improvement one and two years after their big drop and about half three years later.
Here are the 289 players with a more than 5% drop in K%, broken down:
First year Year+1 Year+2 Year+3 Hitters 289 289 219 106 Average Change -6.7% -4.3% -4.2% -3.2% Subsequent Higher K% 213 168 80 Average Increase 3.6% 4.0% 5.3% Subsequent Lower K% 76 51 26 Average Decrease 1.4% 2.4% 2.4%
Of the 289 hitters whose strikeout rate fell 5% or more, 213 had a higher strikeout rate the next season, averaging 3.6% higher. So they gave up some, but not all, of their 6.7% improvement. The regression rate is higher in subsequent years. But, on average, they don’t abandon everything. And some players get even better.
But that’s the problem with averages. This graph shows the distribution of the change in strikeout rate the year after a sharp decline.
That seems like a typical normal distribution…except that 20% of the time, the hitter gives up almost all of his improvement. And that proportion increases to 26% two years later and 35% after three years.
Is the same true for hitters whose strikeout rates rise sharply? There were 254 hitters whose strikeout rate increased by at least 5% in consecutive seasons. The average increase was a reflection of the previous discussion, +6.7%. The biggest increase was Travis Shaw, from 18.4% in 2018 to 33.0% in 2019. However, of the 254, there was less tightness than with players whose strikeout rate fell. After the big increase, these hitters’ strikeout rates were 3.7% higher after one year, 3.5% higher after two years, and 3.5% higher after three years.
First year Year+1 Year+2 Year+3 Hitters 254 254 199 155 Average Change 6.7% 3.7% 3.5% 3.5% Subsequent Higher K% 55 42 32 Average Increase 2.0% 2.4% 2.6% Subsequent Lower K% 199 157 123 Average Decrease 4.3% 4.7% 4.5%
The average hitter who experiences a 5% or more increase in K% gives up a little more than half of the increase over the next three years. But nearly 80% of hitters whose strikeout rate increases by 5% in consecutive years return to their previous rate in each of the next three seasons, recovering about two-thirds of the increase.
And here is the distribution:
Of players whose strikeout rate increases by at least 5% in consecutive years, about 30% return to where they were the following year. Yes, that includes some hitters whose strikeout rate rose 10% one year and fell 5% the next, but it also includes players whose rate rose 5% and then fell 10%.
This is what I think we can conclude:
- Of hitters whose strikeout rate changes by more than 5% in consecutive years, it turns out to be a complete lie for a significant minority. Of the players whose strikeout rate fell by 5% or more, it was back within 1% of its previous level within a couple of years for a quarter of them. Of the players whose strikeout rate increased by 5% or more, it was back within 1% of the previous level for a third of them.
- In the rest, however, there is rigidity. Generally speaking, we can expect a hitter whose strikeout rate jumps from one season to the next to maintain at least half of that increase. More encouragingly, hitters whose strikeout rates drop sharply, on average, remain close to three-fifths of the increase. Given that this analysis came in a generally increasing strikeout environment, that’s impressive. It represents a real improvement. Large changes in strikeout rates are more difficult for hitters whose strikeout rates improve than for those whose strikeout rates worsen.
- But these are averages. Individual rates will vary widely. Ronald Acuña Jr., who currently has a 24.2% strikeout rate after averaging 11.4% last year, seems likely to fall within the first point, not the second.
Thanks to Mike Ferrin not only for the article idea but also for his constant advocacy for analytics and intelligent sports journalism.
Thank you for reading
This is a free article. If you enjoyed it, consider subscribing to Baseball Prospectus. Subscriptions support ongoing public baseball research and analysis in an increasingly proprietary environment.
Subscribe now
2024-05-23 10:27:15
#connections #extreme #strikeout #rate #year #year
