Nolan Arenado: 4 Stats that Matter

It was just about this time last year when the Cardinals acquired Nolan Arenado in a trade with the Colorado Rockies. Arenado arrived in St. Louis with huge career numbers and massive expectations.

It seemed a foregone conclusion that Arenado would fail to meet both.

Simply moving from the offensive paradise that is Coors Field to the pitching-preferred confines of Busch Stadium was enough to gut his offensive stats. Meanwhile, Arenado’s defensive wizardry is not rooted in geography. Cardinal fans, though, watched THE wizard play shortstop and THE Scott Rolen play third, so we’re a bit hard to impress.

Make no bones about it, Nolan Arenado was really good last year for the Cardinals. But I think most fans would agree that they expected him to be better than he was.

I’ve got good news for you. While he’s never going to recover his Colorado numbers, Arenado should be better in 2022. Here’s a 2021 review for Arenado, four stats that matter, and my projections for his upcoming season.

Season in Review

For the year, Arenado clocked in with a 113 wRC+ and a .336 wOBA. That’s solidly above average and ranks 10^th among qualified third basemen in 2021. It is, however, significantly below the standards Arenado has set for himself.

From age 25-28 with the Rockies, Arenado had a wOBA that ranged from .386 to .395 and a wRC+ between 126 and 133. That’s a Hall of Fame level of peak performance during his prime production years when combined with his Platinum Glove-level of defense. Arenado’s fWAR was between 5.0-6.1 every season.

Entering this season, it was difficult to know how those stats would translate. Thankfully, Baseball Savant is in the business of statistical translation. For his career, Arenado has an expected Statcast slash line (xBA, xwOBA, xSLG) of .261/.336/.466. That’s more meaningful to us than his actual Statcast slash line (BA, wOBA, SLG) as a Rockie: .293/.372/.541.

The problem with that expected Statcast slash line is it includes performances we don’t want to include for the sake of this translation – like his well-below average rookie season, his injured 2020, and his Busch Stadium 2021. If we recalculate that to exclude those seasons we are left with an “in-his-prime-and-healthy” in Colorado expected Statcast slash line (xwBA, xwOBA, xSLG). Here’s that line below compared to Arenado’s actual performance from 2021 in St. Louis:

Xstats COL 2014-19: .264/.343/.479
Actual stats STL 2021: .255/.336/.494

Conclusion? By wOBA, Arenado was probably a hair below what fans should have expected coming over from Coors based on wOBA. But this was pretty much an average season for him when giving significant weight to his expected performance throughout his career as opposed to his actual performance playing half his games at high altitude.

With that foundation, let’s look forward. Where does Arenado go from here? Here are four stats that matter:

1. BABIP (Overall Slash & wOBA)

It’s worth noting that by at least one measurement, Arenado should have been quite a bit better than he actually was. His BABIP – batting average on balls in play – was just .249 last year. In most seasons BABIP will normalize for batters at around .295-.300. What caused Arenado to come in nearly 50 points below normalization?

The best answer here is probably nothing. Most of Arenado’s batted ball rates – both standard and Statcast – are within range of his career norms. That includes exit velocity, max exit velocity, barrel rates, hard hit%, etc. There’s variance in those numbers but not enough to explain 50 points of BABIP. Standard batted ball data helps a little. Arenado might have got a little “homer happy” this season – trying to work harder to drive the ball out of the park. His fly ball rate was about 6 percentage points higher than normal. More fly balls in Busch Stadium mean more outs and Arenado did lose 4 HRs compared to expected.

Paul Goldschmidt experienced a similar BABIP drop with a corresponding bump in FB% in his first season in Busch. It didn’t last long for him and he settled back into his normal self by the next year, at least in terms of expected stat translations.

ZiPS and Steamer both believe Arenado will see his BABIP jump significantly. Neither is willing to take him back to league neutral, but ZiPS has him at a .263/.324/.477 traditional slash line with a .272 BABIP. Steamer has him with a .262/.330/.479 slash line with a .265 BABIP and a .341 wOBA. Those BABIP numbers seem very conservative to me. The closer he comes to neutral (or higher, as he was from 2017-2019), the more those slash lines and that wOBA would grow.

Don’t rule out something like a .270/.345/.500 season with a .350 wOBA if he has a BABIP closer to his career averages.

2. 87 wRC+ in August

Essentially, what I’m trying to do above is establish some norms for Nolan Arenado when he’s healthy and not suffering through relatively explainable BABIP issues. Glancing at his split stats helps further solidify some of these norms and also better explain some of the problems with his season.

What follows is Arenado’s wOBA/wRC+ by month for the 2021 season:

April: .322/105
May: .387/147
June: .331/110
July: .337/114
August: .296/87
September: .341/116

You’ll notice that one of those is not like the other. August was not a good month for Arenado. His wOBA and wRC+ were both well below average. His slash line for the month was .212/.278/.433. It was a bad month.

Now, we can’t just wipe that out any more than we can fixate on his .387 wOBA May. However, the other months are informative. For most of the season, Arenado ranged between a .322 wOBA and a .341 wOBA with some low BABIPs mixed in.

That range is relatively small for monthly samples and fits well with the offensive profile we are projecting for Arenado at Busch, with some potential bump in BABIP normalization.

3. BB%

Here’s another area of potential improvement that ties in with his monthly split stats. Arenado’s walk rate on the season was 7.7%. That’s right on with his career average of 7.9%. However, discounting his limited 2020, Arenado hasn’t had a BB% rate below 9.1% since 2015. In his prime-healthy seasons, he went 9.8, 9.1, 10.8, 9.4. Then the dip to 7.5% in short/injured action in ’20 and about the same in ’21.

Which is more important: historical trends or recent trends?

We could debate that for a whole article, but I lean toward historical trends in this particular case. Why? The answer lies in his ’21 split stats. Here’s Arenado’s 2021 BB%’s by month:

Apr: 6.4%
May: 6.0%
June: 8.0%
July: 7.4%
Aug: 8.7%
Sept: 8.6%

Divide those into halves: 1^st half: 7.1%. 2^nd half: 8.4%. Arenado got off to a slow start with the walks early in StL and improved notably as the season went on. He didn’t climb back to his COL levels, but he got close in August and September. ZiPS and Steamer both believe the trend with continue.

With Arenado’s impeccable defense, it really doesn’t take that much extra offense to start ticking his fWAR up toward “elite” levels. A 25-30 point jump in BABIP (which would still leave him below neutral) plus just a 1-1.5% point bump in BB rate to return to his career norms (somewhere between 8.5-9.0%) could give him as much as 1 more full fWAR.

4. Fastball wOBA

Lastly, I have one more stat that I think brings a lot of this together and informs my optimism about Arenado going forward: wOBA against fastballs.

We’ve seen this before. In Goldschmidt’s first season in Busch, his performance against fastballs dropped precipitously. Goldy had a well-established track record of wOBAs against fastballs in the mid .400s. In his first season in StL that fell to .346. It was so far below his norms that some analysts began to wonder if he was losing bat speed.

He put those fears to bed in this shortened 2020 season (.459) and again this season (.415).

Now Arenado has done the same thing, except his fall was even more glaring. Like Goldschmidt, Arenado had a well-established history of crushing fastballs. His average wOBA against the pitch type through his prime seasons would be somewhere in the .425 range. Last season that fell to .306.

Why? What causes a wOBA drop of over 100 points against a pitch type? Was it the residual effect of his shoulder injury in 2020? Was it more of those BABIP issues showing up? Was he too homer (flyball) happy? Or was it just some combination of these things plus a healthy dose of statistical volatility?

Regardless, I have extremely high confidence that at least some of his production against fastballs will return in 2022. Even a bump from .306 to .380 or so – still below his established norms – would mean a ton of extra production from Arenado, since he sees fastballs nearly 60% of the time.

2022 Outlook

When considering the natural decline that Arenado faced coming to Busch from Coors, 2021 really wasn’t that far off his x-stat norms. Some of his weaknesses last season can be attributed to bad habits that don’t seem likely to continue for a hitter of Arenado’s caliber. They are remarkably similar to Paul Goldschmidt and we saw how thoroughly Goldy sorted out his early-StL issues.

We could speculate about why it happened. Or we could let 2021 lie and look ahead, expecting Arenado to settle in the way Goldschmidt did. I have a lot of confidence that’s what Arenado will do, assuming he avoids health issues. With ZiPS holding back his BABIP, I’m actually a little more optimistic about Arenado’s upcoming season. Here’s ZiPS numbers and my projections:

ZiPS Projection: .263/.324/.477, 4.2 fWAR
My Projection: .270/.345/.500, 5.3 fWAR