by: Matthew de Marte – August 15th, 2018

Since the Colorado Rockies began playing baseball in 1993, one thing has always been constant: Coors Field is a hitter’s park. Efforts have been made to tame the great advantage hittes have here. The right field fence has been raised, a humidor used to combat ball flight. One problem that the common fan has when looking at Rockies players is how to accurately evaluate them. Some players who take their talents to Coors and have breakout offensive performances are said to benefit from Coors while others this same narrative is dismissed. In this edition of Short-Stop analytics, I go into detail as to what makes Coors such a hitters park and how to utilize this in player evaluation.

Fangraphs provides a host of different park factors for every park, and Coors, for pretty much every metric, is ranked near the top if not at the top for being the most hitter friendly park. For Fangraphs basic 5 year park factors, Coors Field gets a 116. In other words, playing at Coors Field on average leads to a 16% increase in offensive production, by far the biggest in baseball. So where do these advantages come from?

Fans and analysts who talk about Coors often attribute its run happy environment to the high altitude and it being a launching pad. While Coors does give a ~ 10% boost in home runs, for players who call it their home field that margin is not the highest in baseball. In fact, at this moment there have been 149 home runs hit at Coors this year, which ranks 11th among all parks. This number may be a little low compared to years past due to the Rockies unusually weak offense this year. The point remains the biggest benefit of playing at Coors may not be your home run totals. So, let’s use Statcast to see on what batted balls Coors hitters benefit most from. The following table shows wOBA and xwOBA on batted ball types by league average and at Coors in 2018. We could use numbers for the entire Statcast era, but that provides some complications, and I think it is fair to assume these numbers are fairly consistent by year.

wOBA | GB | LD | FB | xwOBA | GB | LD | FB |

League avg. | .224 | .653 | .444 | League avg. | .225 | .682 | .483 |

Coors | .216 | .708 | .554 | Coors | .221 | .683 | .471 |

So, the differences pop off the charts immediately. Batters are rewarded way more for hitting the ball in the air at Coors than the hitter at the league average park is. For what it’s worth, 2018 is also the first year of the Statcast Era where batters at Coors are not benefiting more than the average player for hitting ground balls. Back to the data above, hitters at Coors Field are benefiting much more from hitting line drives and fly balls then they are expected to. This goes with what you should expect. The following plots show the results of batted balls by exit velocity, and launch angle. The first is for every batted ball from 2015-2017, the second uses the same time frame, but only focuses on batted balls at Coors:

These visualizations can be pretty difficult to interpret so I will explain. The x-axis is represented by Exit Velocity, and the y-axis by Launch angle. The shaded color you see is the batted balls wOBA value. wOBA values for 2018 are as follows ( wOBA values remain pretty constant by year without much drastic change):

- Home Runs: 2.032 or the lights blue
- Triples: 1.579 or a slightly darker shade of blue
- Doubles: 1.248 or a similar shade to triples
- Singles: .880 or darkest shade of blue that is not navy
- Outs: 0 or navy blue

There are a few takeaways from these visualizations. It is very hard to come away with specific things from such a graph, but generalizations that can be further looked into can be seen. For instance, hitters have a little more leeway of hitting home runs not as hard at Coors, and harder hit balls do not follow the same general launch angle guidelines other parks have for home runs. Hitters also have more leeway with how soft they hit their line drives to earn hits, especially doubles.

Now we know the batted balls in the air at Coors are typically more valuable than other stadiums across the MLB, and hitters have more leeway with their EV/LA to produce extra base hits. Let’s look at specific batted ball measurements. The following table splits batted balls at Coors vs League Average separating Line Drives and Fly Balls. The batted balls are then split up by their exit velocity. The first table shows batted balls 95+ MPH, or what is defined as a hard hit ball, the second table shows this data for batted balls hit less than 95 MPH:

Exit Velocity >= 95 MPH.

wOBA | FB | LD | xwOBA | FB | LD |

League Avg. | .909 | .763 | League Avg. | .997 | .813 |

Coors | 1.191 | .865 | Coors | 1.002 | .826 |

Exit Velocity <95 MPH

wOBA | FB | LD | wOBA | FB | LD |

League Avg. | .109 | .542 | League Avg. | .111 | .545 |

Coors | .132 | .550 | Coors | .117 | .534 |

The biggest advantage of hitting at Coors field is how much better batted balls classified as fly balls hit 95+ MPH perform at Coors than other fields. While Coors provides a slight boost on line drives and weak fly balls, hitters are rewarded most for fly balls hit 95 + MPH. The following tables show the breakdown of hit types on fly balls hit 95+ MPH, and batted balls hit between 95-99 MPH:

Exit Velocity > 95 MPH

Venue | Singles | Doubles | Triples | Home Runs | HIt Prob % |

League Avg. | 0.36% | 7.46% | 1.55% | 38.78% | 48.16% |

Coors | 0% | 8.94% | 4.47% | 49.59% | 63.01% |

95 >= Exit Velocty <100

Venue | Singles | Doubles | Triples | Home Runs | HIt Prob % |

League Avg. | 0.29% | 6.75% | 1.11% | 14.68% | 22.83% |

Coors | 0% | 11.01% | 6.42% | 22.94% | 40.37% |

The Coors effect is not just prevalent on Home Runs. Coors significantly increases the rate at which doubles and triples occur. Triples occur at a rate 187% (!!) higher than league average on fly balls hit 95+ MPH! While the ball does carry a lot at Coors, the large gaps also play to hitters advantage giving significantly more room for the ball drop. The most telling signing is how much greater a hitters hit probability is when hitting hard fly balls at Coors compared to other stadiums.

The last bit of information to look at is the following visualizations. They show the difference in wOBA-xwOBA for batted balls by their exit velocity over 95 MPH for coors field, and a league average park by Fangraphs park factors; Wrigley Field is the best park to use based on its factors. Although, it has tiny dimensions the unpredictable wind makes it overall a very average park to play at. The visualizations are as follows:

A picture is worth a thousand words, or in this case two pictures. You are going to run into more extra base hits by hitting the ball hard in the air in Coors. At a league average park such as Wrigley, there are not many exit velocity bins on fly balls where hitters outperform their expected performance and have underwhelming returns in other zones. At Coors, if you hit a flyball 95+ MPH you are going to experience better than expected results. Wrigley is notorious for being a hitters park by some across the league and the visualizations above show it is not close with how much more hitters benefit at Coors compared to Wrigley. We have always known Coors is a hitters dream to hit at, but with Statcast we now have the capability to better quantify how it aids hitters production. I hope article gives you a good understanding of the Coors effect. There can still be great players who call Coors their home. Nolan Arenado could be the NL MVP this year. However, players who call Coors home must have the numbers adjusted for due to the extreme offensive environment. Using Statcast metrics, I think you can truly understand how to quantify the Coors effect and use it in player evaluation. I hope you learned something new from this article, as always reach out to studentsofbaseball@gmail.com if you have any questions!

*All data taken from Baseball Savant*

*Data used is from all games through August 14th*