Fun With Sample Size: Why You Shouldn’t Worry About Struggling Superstars

Let's have some fun with sample size!

*All 2020 stats in this article are as of the end of August 2, 2020*

2020 is a historically strange year for baseball. As opposed to the offense-heavy 2019 season, the bats seem to be a little slow to warm up. Some of this can be attributed to the shortened spring training warm-ups. It could also be attributed to different approaches at the plate due to the shortened season. Another explanation is the craziness of everything going on affecting play. While it may be a little of all of those things. Let’s look at why it’s probably sample sizes that are to blame for the quiet bats.


Who needs pitchers that can’t hit when you can have DHs that can’t hit from r/baseball


As case studies, we will use the struggling superstars, Christian YelichRonald Acuña Jr., and Cody Bellinger. All three of these players had monster years in 2019 and for good reason. They were being drafted in the first couple of picks for the confidence in their bats. However, 2020 has not been kind to these three elite bats.


Christian Yelich

2020: .037/.071/.148/.220 (6 games)


Yelich was taken first overall in quite a few drafts, and it’s easy to see why. He had a monster 2019, and two back-to-back years with a 1.000 OPS or higher! Then, what should we make of his absolutely abysmal .220 OPS so far in 2020?


<a href=Christian Yelich’s 2019 OPS by Sample Size” width=”900″ height=”545″ />


Looking at the plot, there is, of course, a ton of noise in the six-game OPS sample. This is entirely to be expected. At his worst, Yelich had a .359 OPS across a six-game sample! That’s better—but almost to an irrelevant degree—to his 2020 OPS through six games. As you can also see, his 60-game OPS sample is pretty consistent with his season-long OPS. At a visual level, we already shouldn’t be that worried about Yelich.


Christian Yelich’s Worst 2019 OPS by Sample Size


If we want to go beyond the sample sizes, he has a .000 BABIP. Literally. A ZERO BABIP! I don’t have to explain to you why that will normalize statistically. He has had over a .336 BABIP in every single one of his major league seasons. The only worrisome note for Yelich is that his plate discipline has been awful so far in 2020. He consistently has around an 11% walk rate and a 20% strikeout rate, and right now, those numbers are 3.6% and 42.9%, respectively. Yelich could be trying to swing at a lot of bad pitches to break out of the “slump”, but honestly, I wouldn’t put much into this at all. He’ll be fine.


Ronald Acuña Jr.

2020: .195/.283/.366/.648 (10 games)


Acuña hasn’t been as bad as Yelich has so far in 2020. Even though a .648 OPS is still not where Acuña will finish, it is still respectable, albeit poor. Like Yelich, Acuña’s OPS has sat at around .900 for the past two seasons.


<a href=Ronald Acuña Jr.’s 2019 OPS by Sample Size” width=”902″ height=”555″ />


There is way more noise in Acuña’s profile than Yelich. The point is that he is a bit more of a volatile and streaky hitter than Yelich. Why couldn’t one of his cold streaks be now? Especially considering that we see the 60-game OPS largely adhere to the season-long OPS. The trend of the 60-game sample size being pretty close to the full-season sample size should come into focus by this point. Acuña’s worst ten-game sample OPS is actually pretty close to Yelich’s worst six-game sample from above. Not to mention, it’s better than Acuña’s 2020 so far, so if this is the worst of him in 2020, he’s already better off than 2019.


Ronald Acuña Jr.’s Worst 2019 OPS by Sample Size


Moving beyond the sample sizes yet again, he hasn’t stolen a base in 2020 so far, and that is disappointing. However, the fly ball rate and hard contact rate are about where they always are. On top of that, Acuña is hitting more line drives and less grounders so far in 2020 than in past seasons. This will certainly help that average climb a ton. As with Yelich, the strikeout rate is a bit elevated. Regardless, he’ll be fine.


Cody Bellinger

.150/.209/.250/.459 (9 games)


Lastly, we get to Bellinger. Like Yelich and Acuña, he was drafted early in the first round and is struggling at the plate thus far in 2020. There are some differences between Bellinger and the other two struggling superstars that will be elaborated upon below, but otherwise, he is struggling all the same.



Bellinger is a unique case in that his 60-game OPS is much more separated from the season-long OPS than the other two case studies. This is likely due to his remarkably hot start. This is confirmed when you see the negative regression in the data over the course of the season. Just as he regressed to a human level in 2019, he will regress to a superstar player in 2020. Again, his worst 9-game sample OPS in 2019 is horribly bad at .549. It’s also interesting that his worst OPS for the 60-game sample was a solid .836 even though his average was just .239.


Cody Bellinger’s Worst 2019 OPS by Sample Size


Similar to Yelich, the BABIP is half of what it has been for the entirety of Bellinger’s major league career. Unlike the other two, his strikeout rate is actually the lowest it has been in his major league career so far. The walk rate is also the lowest. It seems that Bellinger is trading walks for making contact. The hard contact and line-drive rate are down, which would be concerning if not for the sample size. This is even less concerning when you see that the line drive rate is 5.9%, which even for the worst of hitters is unsustainably bad. One mark of consistency in Bellinger’s batted ball profile is the fly ball rate. If you haven’t figured it out already, he’ll be fine.


They’ll be fine.

Lucas Zenobi

Lucas Zenobi is a graduate of the University of Pittsburgh and a life-long Pittsburgh Pirates fan. His other interests include film, music, and any and all things Pittsburgh.

One response to “Fun With Sample Size: Why You Shouldn’t Worry About Struggling Superstars”

  1. Jackie T. says:

    Acuna did get a steal on Tuesday. Glad to know he’ll be fine since I took him #1 overall …

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