In my last post I talked about Gary Sanchez and his 2020 struggles at the plate. I cited his excellent batted ball statistics persisting in 2020 and the main reasons for his demise being attributable to a bloated strikeout rate that is bound to regress and some bad luck on balls in play. After further reflection, my stance on his exceedingly low BABIP has not changed. It was one of the worst figures of the past five seasons and given how hard he hits the ball when it is put into play, I do not expect anything close to that figure to persist. Even though he hits the ball with so much authority, Sanchez may always post lower BABIP figures due to his propensity for hitting fly balls and the proportion of his hits that are home runs (home runs are not included in BABIP), but nevertheless there will be some positive regression on this front.
The strikeout rate requires more nuance. I noted his slight improvement in his approach; he improved his chase rate and swung at more pitches in the strike zone in 2020. His overall swing rate did not change much and he saw a slightly higher percentage of pitches in the strike zone. The issue was his contact rates, both inside and outside the zone. His zone contact rate declined a little bit from an already unimpressive figure, but the larger issue was Sanchez, relative to league average, could not put the bat on the ball when he chased. This meant that even though he was chasing less, his rate of contact when he did chase was such where swings on pitches outside of the zone had an outwardly bad effect on his results. I also included some analysis on the probability that this increase in strike out rate was purely the result of variance and found there was some non-zero possibility that this was the case. I threw the improved approach, substantial negative regression in contact rates, and variance into a blender and concluded that he was bound to be much better in the strikeout department in 2021.
Thinking more about the strikeout issue, I thought I failed to offer context behind Sanchez's rising strikeout rate and look at other players who saw large changes in strikeout rate and how they fared in later seasons. It is easy to say that any massive increase in strikeout rate should be followed by a corresponding decrease towards the players "true talent".
I pulled data on every set of three hitter seasons since 2015 where the hitter had at least 150 plate appearances in each season. I then took the calculated the changes in strikeout rate between year N and year N-1 and between year N-1 and N-2.
Positive integers indicate increases in strikeout rate, which are generally bad for hitters (but not always, could be an indication of a hitter being more selective or selling out for some power). As you can see in the direction of the trend line, increases in strikeout rate are often followed by decreases the following season. When you isolate Sanchez, the results are concerning:
This is the same set of points with Sanchez highlighted. You do not want to find yourself on the top right of this chart, which indicates multiple seasons where your strikeout rate increased. Sanchez's 2020 is especially ugly in this regard. I will not that his 2019 season looks bad in this visualization, but in 2019 Sanchez posted his best numbers on contact. That might indicate that he was selling out for some power coming off a down 2018 season. Using the data presented above, I built a simple linear model predicting a player's change in strikeout rate. The model had two inputs: the prior change in strikeout rate and the player's age (we know changes in strikeout rate are partly a
function of age). After fitting the model to the data, I wanted to look at how Sanchez looked in 2019 and 2020 relative to expectation (i.e. the output of the model). In 2019, based on changes from 2017 to 2018, we should have expected Sanchez to trim 0.57 percentage points off of his strikeout rate while in actuality he added 3.47 percentage points. In 2020, we should have expected him to lose about 0.72 percentage points off of his strikeout rate. Instead, he added eight percentage points. His 8.72 percentage point change over expected was in the 98th percentile in the entire sample. His two year total change is 7th in baseball from 2018 to 2020. Furthermore, I built another model that gauged the probability of a player trimming his strikeout rate based again on age and prior year strikeout change. Sanchez again sticks out.
Player seasons in the top right quadrant are disappointing relative to expectation. Sanchez both seasons was expected to trim his strikeout rate and he did the opposite. I will note that most of the seasons where players added to their strikeout rate much more than expected came from 2020, due to the small samples. Still, I think there is some reason to be concerned with Sanchez and his increasing strikeout rate. If he wants to return to his 2019 level, he is going to have to buck the strikeout trend. Sanchez will be 28 going into next season and has been a major league regular for about four years now when you account of the fact that he did not play full seasons in 2016 and 2020. He is probably not going to get better from a batted ball perspective at this point;
exit velocity peaks in a players mid 20s. Improvements will have to be made in his contact rates and correspondingly his strikeout rate. Whether or not he has the ability to make these improvements will largely dictate whether or not the Yankees tender him a contract going into his second year of arbitration.
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