The next thing we need to do is look at players who started their career with the Rockies, were starters for a few years and then went on to play elsewhere. I initially used wRC+ as the main stat to compare here and I’m going to continue doing so. If Coors Field really makes a hitter better, then even after adjusting for Park Factors then we should see a player’s wRC+ go up after he leaves the Rockies. So let’s look at the following players:
Here is a comparison of how they did season by season in terms of wRC+:
Since I initially tweeted this, I’ve gone back and gotten each player’s total wRC+ for when they were Rockies, after they played for the Rockies and what their total career wRC+ is to see how much difference there actually is. We’re only looking at players who had consistent starting time over about 3+ seasons so that we have more than enough data points to give us a full circle view. Take a look:
In each case (besides Tulowitzki), the player’s wRC+ jumped up AFTER they left the Rockies. It could be because they were younger hitters and were still developing when they were with the Rockies or simply because wRC+ assumes all road games are neutral sites (so Rockies players get dinged a little more for this because they play in extreme pitcher parks like Petco Park and Oracle Park).
The other part we need to point to is the fact that these hitters didn’t have to make those constant adjustments in approach that we talked about earlier. That alone will generally lead to a slight increase in wRC+. With all these factors, we see players generally get a little bit better when they leave the Rockies, alluding to the point that Coors does not make a hitter immediately better.
And we can only really choose five players here. As anyone who’s been a fan of the Rockies can tell you, it’s been tough to find players who had consistent starting time with the Rockies that continued to get consistent starting time with other teams. They’re either Rockies for life or they struggle elsewhere and there’s really no in-between.