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Nolan Arenado and the Coors Effect

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How will he hit now that his home park isn’t in Denver?

Photo by Denis Poroy/Getty Images

News item: Rockies star Nolan Arenado is about to be traded to the Cardinals:

MLB Network insider Ken Rosenthal reported Friday night that the Cardinals have agreed to acquire Arenado from the Rockies in a deal that will involve cash and multiple players. Two Major League sources told MLB.com that nothing is final, and a source told MLB.com’s Mark Feinsand that a deal might not be completed before the end of the weekend, because there are several issues that must still be addressed before the trade can become official.

So while we wait for this deal to be finalized, let’s talk about the Coors Effect — the fact that in general, the Rockies’ home park in Denver tends to increase offense.

And it is true that Arenado, through his eight-year career, hit far better in Denver than elsewhere:

Arenado at Coors: .322/.376/.609, 2,303 PA, 136 home runs
Arenado on road: .263/.322/.471, 2,255 PA, 99 home runs

Oh.

Arenado away from Denver is still a pretty good player — .793 career OPS — but those are not the perennial All-Star numbers (.985 OPS) he’s posted at Coors Field.

The difference is significant enough — nearly 200 OPS points — that it’s worth examining how Arenado might do now that he’ll be playing 119 games a year in NL Central parks (81 in St. Louis, 38 in other NL Central parks) instead of that many in NL West parks.

Here are Arenado’s lifetime numbers in Busch Stadium. Of course, he was facing Cardinals pitchers there; now, he’ll face other teams’ hurlers in St. Louis:

.278/.337/.511 (25-for-90), five home runs

Obviously that’s a small sample size, but the .848 OPS is higher than his overall road OPS.

What about the other NL Central parks?

Miller Park: .397/.461/.838 (27-for-68), 1.299 OPS, eight home runs
Great American Ball Park: .291/.370/.456 (23-for-79), .825 OPS, three home runs
Wrigley Field: .247/.287/.495 (23-for-93), .782 OPS, five home runs
PNC Park: .269/.310/.358 (18-for-67), .668 OPS, one home run

Small sample sizes again, and all over the place. How about putting those all together, the NL Central as a whole (including St. Louis)?

.292/.349/.528 (116-for-397), .877 OPS, 22 home runs

That’s right about the midpoint between his current home OPS and current road OPS. Obviously he’d be facing different pitchers than he has in the past, many more from the NL Central than the NL West, and eventually he’d likely improve his numbers in Busch Stadium once he got accustomed to the different aerodynamics of how a baseball moves in St. Louis (466 feet above sea level) than Denver (5,280 feet above sea level).

We don’t have a lot of data on star players traded away from the Rockies in recent years in order to figure out what this effect might be on Arenado. The biggest star dealt away by Colorado recently is Troy Tulowitzki, and Tulo’s decline was largely due to injuries, not absence from the elevation in Denver.

There’s also the example of Corey Dickerson, who left the Rockies after three pretty good years there (.879 total OPS, 1.077 OPS in 477 PA in Coors Field). Since leaving the Rockies after 2015 he’s posted an OPS of .801 in 2,199 plate appearances, and in the two parks he’s played in most, outside of Coors: .749 OPS in 564 PA in Tropicana Field, .824 OPS in 344 PA at PNC Park.

Then there’s DJ LeMahieu — and I have no explanation for what he’s done. Not only were LeMahieu’s numbers not affected negatively by leaving Coors Field as his home park, he actually got better — a lot better — as a Yankee. He does love to hit at Yankee Stadium — he has a career 1.042 OPS there in 429 PA. Maybe he’s the proverbial “exception that proves the rule.”

Granted, this is anecdotal evidence, and I do not purport it to be any sort of detailed scientific or statistical study. But there does appear to be some truth to the claim that players who have played a long time with Coors Field as their home park do have some offensive decline when they leave. It’s also true, though, that in general players’ OPS drop about 30 points on average from home to road, likely due to all players being much more familiar with their home ballpark. From 2017-19, overall home OPS was .770, road OPS .740.

Here’s a FanPost from our Rockies site Purple Row that takes a somewhat deeper dive into Coors Field and what it does to hitting — based on the time of year, interestingly. And here’s a 2014 Fangraphs article that suggests “regression to the mean” happens to players who leave Coors Field as their home park.

One other thing Arenado will see more of now that he’s in the NL Central: righthanded pitching. The NL Central has almost no lefthanded starters. Overall Arenado has an .852 OPS (3,323 PA) vs. RHP, .996 (1,235 PA) against LHP.

Prior to the abbreviated 2020 season, Arenado had an .897 career OPS. Given how he’s hit outside Coors Field and some anecdotal evidence from at least one other player, I’d expect that OPS to drop perhaps 50 or so points with him having Busch Stadium as his home park.

He’ll still be a really good player offensively, and he’s the best defensive third baseman in the game. But I don’t believe he’ll put up the superstar numbers he did in Denver.