Examining the Coors Effect | The Process Report

Examining the Coors Effect

One of the “yeah, buts” I briefly mentioned in my last piece looking at hopeful addition Corey Dickerson, at the time, regarded his pretty large splits at home and on the road. Of course his home is a haven for offense of all kinds. Slappy hitters, power hitters, nobodies, they all hit at Coors. All of them hit worse on the road. New research is starting to show, though, that their performance on the road suffers from an unseen penalty after all those games in the Rocky Mountain air. The theory is that the ball breaks differently on the road and the batters aren’t used to seeing that type of movement hurting them more than their opponent. You can Google plenty of prior research, but below you’ll find mine.

I started by isolating all of the players that had at least 200 PA at Coors Field and on the road while playing for the Rockies. I further filtered by eliminating the guys that had never played for another organization. This yielded 44 players with all sorts of different stories. Here are some relevant statistics for these guys when the played at home and on the road as a Colorado Rockie (Rocky?):

Rockies HR

No big surprises here. We knew these guys hit better at home than on the road, though the gap is probably wider than most people realize nearly across the board. What about when these guys played for another organization:

Others HR

Well ain’t that something. These guys that showed such enormous home/road splits while playing for Colorado showed almost no split once they left for greener pastures. In many instances they actually hit better on the road with their new club. To make comparisons a little easier we can index these values where 100 equals average and anything above or below is the percent difference. It’s probably easier just to show you:

Team splits

The first row shows that when these guys played for Colorado they showed around a 24% higher batting average, 25% higher wRC+, and 38% higher ISO when playing at home versus on the road, to name a few. When these same guys played for other teams those splits basically disappeared, such that, their performance wasn’t really all that different whether sleeping at home or in a hotel. That is pretty enormous and something you probably surmised using the above tables.

Another thing you may have noticed is that not only did they hit worse at home, which is pretty expected, but they actually hit quite a bit better on the road, relative to their performance with Colorado. Here’s a look at at that using indexed values, again:


Home Road splits

Here we’re comparing their home and road splits from their tenure with the Rockies to when they were anywhere else. We see that Coors inflated their road split around 20% in batting average, 11% in wRC+ and 14% in BABIP, to name a few. The group hit around 5% better on the road when they were wearing the cap of any other team. This means that while Corey Dickerson certainly won’t bring the park with him it should lead to more success when he’s on the road. Let’s take a look at what he has done in that regard:

Observed normalized

He’s not dissimilar from his peers in that he does have a gigantic split between his home and road figures, but if we adjust for this using the table above we can get a sense for a normalized view of his output. I’d argue that this doesn’t do enough to deflate his home line and you wouldn’t have to try hard to see him having better road numbers with the Rays. Afterall, we’re dealing with the aggregate of 44 wildly different players. Some adjusted better to their second life and some withered and died.

It’s natural to be apprehensive about the very large home/road platoon split that Dickerson has showcased throughout his brief career, but I think the research shows that there is good reason to believe that he will still be a quality hitter even after he comes off the mountain and makes a new home on the beach. He certainly could have asked for better digs. We all know how much the Trop suppresses offense so it’s not like he’s taking a walk down a gentle hill. He’s taking a dive off the pier and hoping that the water is deep enough for him.

The best projection system out there was created and is maintained by Dan Szymborski and goes by the name Zips. Dan was kind enough to post Dickerson’s projections for our viewing pleasure:

The sticker shock of the Trop is in full display as his average and OBP go to basically league average, while still showing a very strong SLG. I asked him to profile Dickerson in a neutral park since the Trop does no batter any favors and he was kind enough to post the line above. When the Rays play in Fenway or Camden or New Yankee Stadium or the Rog the Rays are going to have a nice shiny new weapon to unleash even if the gains are less evident at first blush. Join me in the excitement, because it’s pretty rare that the Rays focus on an offensive addition.

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