If you’ve been following baseball in 2021 you’re aware of the declining batting averages and talk of how the baseball is different in 2021 from previous years during the Statcast era. If you haven’t been following baseball this year, after the 2019 season that saw a spike in home runs, the MLB commissioned a committee of scientists to study the baseball. In short, the committee found that there was less drag on the baseball than previous seasons due to inconsistent seam heights and that caused a surge of hitting productivity. For greater detail on that story from Mark Feinsand of mlb.com, you can read that here. Through May 17th of this year the MLB batting average was .236, the lowest in MLB history behind only 1968’s .237. The lowest batting average in the Modern Era was .248 in 2018. With all of this information in mind I set out to see how this ball is performing compared to previous seasons in the Statcast era (2015-2021).
Per mlb.com a Barrel is a batted ball with the perfect combination of exit velocity and launch angle, or the most high-value batted balls. (A barrel has a minimum Expected Batting Average of .500 and Expected Slugging Percentage of 1.500.) To quickly pare down how the ball is performing I compared how Barrels in 2021 are performing from April 1st to May 17th to the seasons of 2015-2019. The 2020 season did not start until July 23rd so there was no data available for the dates that we’ve played so far this season. The reason for using the same dates rather than the full seasons is that as the temperatures warm the ball will become more hitter friendly. For instance, the HR rate through May 17th 2019 was .542 but for June, July, August and September those HR rates jumped to between roughly .600 and .650. Below is a comparison of 2015-2019 Barrels to 2021 Barrels.
As we go through the data we can see that the 2021 Barrels are under-performing in distance, Batting Average on contact (BAcon, HR%, Slugging% and Batting Average on Balls In Play (BABIP) to all seasons except one; 2018. In those categories, 2021 and 2018 are a near perfect match. Given that the Barrels in ’21 and ’18 were performing nearly identically but the batting averages and SLG. were .236/.394. and .246/.407, respectively, I decided to examine how the next classification of hard hit balls were performing to see if I could uncover why there is such a disparity in batting average. This next classification on baseballsavant.com is called “Solid”.
There are some subtle differences here. The average, 2B, 3B, HR and BABIP rates are all down slightly. The Slugging% is a little more pronounced with a 55 point gap. Since the BABIP and HR rates are very close on the balls with the best kind of contact this led me to believe that the differences in performance must be coming from the lesser hit balls. These lesser hit balls are weaker fly balls, grounders, pop-ups and low launch angle line drives. On baseballsavant.com these are classified into four categories called, “Flare/Burner”, “Poorly/Under, “Poorly/Topped”, and “Poorly/Weak”. For this study I will be labeling this classification as “Lesser Contact”
Once again, the differences are very slight. However, considering the fact that the vast majority of all baseballs that are hit fall into the above classification (51,716 of 60,278, or 85.8%); 9 point spreads in BAcon and BABIP, as well as a 17 point spread in SLG%, start to take on a much bigger meaning. 99.8% of these balls are in the field of play so there must be something going on with the BABIP. Let’s again did a little deeper.
*Please note that I did not include the distance in the above data set. Unfortunately, in 2018 there were 2,234 balls where the distance was not tracked. These were predominantly pop-ups and therefore rendered the distance comparisons useless.
For both ’18 and ’21 the BABIP on line drives were nearly identical despite an uptick in shifts and strategic positioning rates (SFT/STR%). Nothing to see here.
This becomes a little more interesting. The outfield shifts and strategic positioning rates dropped from 9.06% in ’18 to 6.90% in ’21 and the BABIP on those balls rose from 0.106 to .126. It’s not a huge number but it’s something. However, this a POSITIVE bump in BABIP for 2021, not a negative one. What exactly are you doing with my time here Stat Boy?
Well look at this. In 2018 MLB teams deployed an infield shift or strategic positioning alignment on 24% of all ground balls hit (14.75% vs RHB and 41.12% vs LHB). This resulted in a .249 BABIP. In 2021 MLB teams have used an infield shift or strategic positioning alignment nearly 40% of the time that ground balls are hit (25.09% vs RHB and 62.21% vs LHB!) and this has resulted in a 20 point drop in BABIP down to .229. This is big, folks. Let’s take a look at how shifting as a whole has impacted BABIP in 2021.
All Batted Balls In Play
The shift or strategic positioning rate has gone up on batted balls in play from 31% in 2018 to 47% in 2021 and the BABIP has gone down from .294 to .286.
What Does it All Mean?
There are definitely some pretty significant differences in the performance of the 2021 ball versus 2015-2017 and 2019. However, when compared to the 2018 ball, the differences are marginal. On Barrels, there’s basically no difference. On Solid contact there is a slight depression in thump (.08 in HR’s and .055 in SLG). These are pretty small, but they’re there and they count. The huge difference between 2021 and 2018 are the shift and strategic positioning rates. The scouting reports and the defensive deployments that follow are accounting for about an 8 point drop in BABIP between the two seasons. This is a loss of about 229 hits or .006 batting average points. Another aspect of the game that’s changing are the strike out rates. In 2018 it was 22.5%. In 2021 it is 24%. With the BB% remaining virtually constant that means that 1.4% more of all PA’s end in a strikeout. That’s 650 AB’s this year with a 0.000 batting average that did not occur in 2018. The impact? A loss of about 160 hits versus 2018, or .004 batting average points. So, in summary, the ball is basically the same as 2018 (Previously the worst ball in the Stacast era) with a negligible difference in HR rate on hard non-barrel contact. The real differences in the landscape (At least versus 2018) can be accounted for by increased shifts and increased plate appearances that end in strikeouts. 60% of the drop in batting average is due to shifting and 40% is due to an increased K%.