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Understanding the impact of Coors Field

By: Tom Tippett
Date: July 16, 1996

As you know, offense goes sky high in Coors Field. We can see that in the park factors and the home/road splits for individual players. Here are some hitting stats for the NL as a whole (including Coors), Coors only, the NL without Coors, the Coors numbers prorated to 700 plate appearances, and park-adjusted norms for players who play half their games at Coors.


                 NL                 w/o       Per      Half

              Total    Coors      Coors     700PA     Coors

G              1007       72        935       162       162

AB            69049     5194      63855       638       638

H             18184     1637      16547       201       183

2B             3367      305       3062        37        34

3B              418       59        359         7         5

HR             1917      241       1676        30        23

W              6668      509       6159        62        62

K             13309      880      12429       108       116

R              9329      975       8354       120       102

AVG            .263     .315       .259      .315      .287

SPC            .408     .536       .397      .536      .464

Runs/Tm/Gm     4.63     6.77       4.47                5.62

What can we learn from this? Quite a bit, actually:

If Coors Field wasn't part of the 1995 NL, the league batting average would have been four points lower and the slugging average would have gone down by eleven points. If you're playing in a Diamond Mind draft league that uses NL players but doesn't include Coors, you can expect your league averages to go down by the same amount.
Similarly, if Coors was not included in your draft league, the league average runs per game would go down by .16 runs. Factor in the unearned runs, and you can expect to see the league ERA go down by fourteen points.
The fourth column is the most compelling. It says that an average hitter with the opportunity to play 162 games in Coors Field would pile up MVP-type numbers. And this is not Barry Bonds we're talking about. This is the average hitter, including pitchers, middle infielders and September callups. Everybody.
The fifth column helps us evaluate real-life players who played in Colorado last year. It's a 50/50 weighting of the Coors numbers in column two and the non-Coors numbers in column three, prorated to 700 plate appearances. These are the figures that the average hitter would compile in 81 games at Coors and 81 games at the other thirteen parks. In other words, any Rockies player who posted those numbers (or the equivalent for the amount of playing time they really had) is merely average. If you move them to another park, you can expect their numbers to drop quite significantly. Keep this in mind when you evaluate your draft choices next time around.
Several members of the 1995 Rockies posted great numbers that were largely dismissed because of the park effect. Was this fair? Looked at in this light, it's clear that Burks had a below-average year. Castilla and Galarraga were a little above average. Bichette had a very good year and deserved consideration for the MVP award. Even if he played in the average non-Coors park, he would have hit about .312 with a slugging average of .553, numbers that compare favorably with Bonds, Gant, Sanders, Sosa, and Conine. I'd make a roster spot available for him anytime.
If the Rockies had played in a neutral park, their pitching staff would have finished around fourth in the league in ERA and their hitters would have been around ninth. So although they ranked last in pitching and first in hitting, it was superior pitching that carried them to the playoffs.