Fun With Sample Size 2: Why You Shouldn’t Worry About Struggling Superstars

Checking back in with our struggling superstars

**All stats are as of the end of all played games on August 29, 2020**

Back at the beginning of the season, I looked at the struggles of Christian YelichRonald Acuña Jr., and Cody Bellinger. All three struggled out of the gate, and I blamed the majority of it on the less-than-a-dozen-game sample size. While that still may be the case, it’s worth revisiting those three players to see how things have gotten better, worse, or stayed the same with a slightly bigger sample size.

As a starting point, it might help to look at the league-wide decline in offense as a frame of reference. In 2019, the league average slashline was .252/.320/.435 with a .320 wOBA and a .378 wOBACON. In 2020, the league average slashline has dipped ever so slightly to .244/.320/.418 with a .315 wOBA and .367 wOBACON. As a whole, the batted ball statistics for the league are pretty similar to what they were last year, and in some respects, they are better. Yet, this leads to some inconsistencies that are likely due to the smaller sample size and would regress in a larger sample. For example, Barrel % and Hard Hit % are up, but average exit velocity is slightly down. Another example is that the chase rate is down, but the K/PA is up. All of this to say that, for the most part, we aren’t looking at a league-wide decline in hitting ability in 2020.

League Batted Ball Statistics

Then, where does that leave our early-season struggling superstars?


Christian Yelich

Part 1: .037/.071/.148/.220 (6 games)

Now: .202/.326/.486/.812 (30 games)


In the first part of this look at sample sizes, Yelich was probably the one struggling most. He had an abysmal .220 OPS coming off of two back-to-back 1.000+ OPS seasons, so the contrast was startling to say the least. Now, Yelich is steadily climbing back to his previous self. The OPS is over .800, which is great to see. Last time, we looked at Yelich’s worst six-game sample size in 2019. Logically, we’ll now look at his worst 30-game sample in 2019 compared to where he is at now in 2020.

Christian Yelich’s Worst 30-Game Sample Size

Even though 2020 is still worse than his worst 30-game sample in 2019, they really aren’t that far off. In fact, Yelich’s slash in the 24 games since that article was written is .256/.396/.598/.994. In 2018, Yelich had a .402 OBP and a .598 SLG, yielding a 1.000 OPS. This is almost exactly the same. It’s true that the average is much lower than expected for Yelich, but his line drive percentage is actually slightly higher than it was last year. I would expect the average to be the next thing that starts to climb back to normal for Yelich. Otherwise, the low walk rate and high strikeout rate that we saw last time has almost normalized, and he is absolutely crushing the ball. His average exit velocity is pretty much exactly where it was last year (good for the top 5% in the league), and the hard hit rate is even higher than last year. I would count on Yelich finishing strong in 2020 with a slash that looks like typical Yelich.


Ronald Acuña Jr.

Part 1: .195/.283/.366/.648 (10 games)

Now: .256/.376/.526/.902 (22 games)


Acuña was doing the best of the struggling superstars in the first iteration of this piece. It was definitely not what we thought Acuña would be, but it wasn’t as shocking as Yelich’s drop off. It’s almost not even necessary to dig in deeper here as looks just about as good as he did in 2019. Sure, the average is slightly lower than usual, and the power and speed has taken a moderate step back. However, his hard contact rate, sprint speed, and average exit velocity are as strong as ever, and the line drive rate is unsustainably high. It’s fairly shocking that Acuña’s batting average is as “low” as it is. When the batting average regresses, expect the steals to return as well.

Ronald Acuña Jr.’s Worst 22-Game Sample Size

His worst 22-game sample in 2019, was nowhere near where he is currently at in 2020. Acuña has returned to his elite self, and in the 12 games since the last piece was written, he has a slash of .324/.468/.703/1.171. From where he was, this is to exact opposite end of the spectrum.


Cody Bellinger

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

.224/.302/.463/.765 (34 games)


My biggest regret in the first iteration of this look at sample sizes was not mentioning Bellinger’s swing change. Kyle Horton went through the details on the swing change at the beginning of the season and why Bellinger might change his swing coming off of his best season. This swing change could have been a key to Bellinger’s struggles, and even though the aim of these looks is at sample sizes, this are the kinds of things that can throw statistical regression out the window.

Revisiting Bellinger, it is sort of shocking how similar his numbers look to his 2018 season.

2018 Bellinger vs. 2020 Bellinger

Almost every single aspect of his batted ball profile looks similar. The major difference is in the BABIPs. In 2018, Bellinger had a BABIP of .313, which is the highest of his career albeit not by a large margin. In other words, it’s within the realm of possible outcomes for Bellinger. In 2020, he has a .212 BABIP, which is absurdly low for him. Without a doubt, I expect the batting average to climb from .224. It’s possible that you will not see a .300+ average again in 2020, but a .267 or .260 (his 2017 and 2018 averages) are likely possible outcomes.

Now, let’s look at his worst 34-game sample in 2019 versus where he is at now.

Cody Bellinger’s Worst 34-Game Sample Size

Alas, it is pretty darn close. This may be a less meaningful comparison than the other two players. Bellinger struggled in the second half of last year with front-loaded production. He certainly could not maintain the pace he was on, but the disjointed halves of 2019 don’t necessarily instill confidence when his worst 34-game sample in 2019 looks like where he is at now. On the other hand, the streaky nature of his 2019 season could lead you to believe he will have a hot streak at some point in 2020 and be back to his 2019 form.

Speaking of streaks, Bellinger’s slash in the 25 games since the last iteration is .255/.340/.553/.893. It’s not as lopsided of a transformation as Yelich or Acuña, and with the similarities to 2018, I have the least confidence in Bellinger to return to 2019 form. With that being said, his 2018 slash was .260/.343/.470/.814. Aside from the power, that is almost exactly the same. I would not be surprised if he finished with a line similar to 2018 with more power.


Images courtesy of Icon Sportswire / Adapted by Michael Packard (@designsbypack on Twitter & IG)

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 2: Why You Shouldn’t Worry About Struggling Superstars”

  1. Moelicious says:

    No mention that Yelich’ K% is 50% higher than his career (30% vs. 20%)?

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