(Associated Press)
This season, the MLB All-Star Game will be played in Miami, and among heavy controversy, the fans will once again vote on the starters. And once again, Cubbies line the first return of the NL ballot. One of these Cubs players that is slated to start in the All-Star Game is reigning NL MVP, third baseman Kris Bryant.
Every year after the All-Star ballots return for the first time, debate arises over who deserves to start and who leads the ballot because of their popularity. And once I saw Kris Bryant had the most votes among NL third basemen, I knew conversation would ensue debating whether Bryant or Colorado Rockies third baseman Nolan Arenado should start for the National League All-Star team.
However, this article is not about Bryant vs. Arenado. It is about the Coors Field Effect. Regardless of where you stand on Bryant vs. Arenado, something that is bound to come up in any debate regarding any Rockies player is how the high altitude affects hitters. How much of an advantage is it for Rockies hitters to play in the Mile-High City? How extensively are the statistics of hitters who call Coors Field their home ballpark boosted by the high altitude?
First, I thought it would be a good idea to cover the science behind the Coors Field Effect. Why do baseballs fly farther at Coors Field than at, say, Fenway Park?
When a baseball is in flight, many forces act upon it, determining how far it travels. One of these forces is the drag force. When the ball is in flight, “a stream of air molecules collides with the surface of the baseball, pushing the ball backwards.” This force, the drag force, is also known as air resistance. This air resistance results in a net force in the opposite direction as the movement of the baseball, preventing the ball from traveling its largest potential distance. In other words, a baseball that travels 300 feet with air resistance could travel 500 feet without air resistance.
Altitude and air density vary inversely. This means that Coors Field, which has the highest altitude of any baseball stadium by over 4,000 feet, has the lowest air density by a considerable margin. This lower air density results in a reduced drag force. Because Coors Field has about 82% of the air resistance that Fenway Park has, it has about 82% of the drag force that Fenway has. What does all of this mean? Fly balls will travel about 5% further in Coors Field than at Fenway Park, which is only about 20 feet above sea level. (For more information on the physics of baseball in Colorado, click here.)
Now that you know the physics behind playing baseball at Coors Field, it is time to determine how much of an effect the reduced air resistance has on hitters’ statistics when they play in Colorado. To do this, I looked at the home/road splits for a few Rockies hitters and the numbers for hitters in their division that have had a significant amount of at bats at Coors Field but don’t call it their home.
(Rich Schultz/Getty Images)
First, Nolan Arenado. The Gold Glove and Silver Slugger winner at third base for the NL last season, Arenado is having an MVP season so far, but how much of that is due to the Coors Field Effect. Over his career, Arenado is slashing .306/.354/.578 with 71 home runs and 255 RBIs in 1192 at bats at home. On the road, he is slashing .264/.311/.468 with 52 home runs and 155 RBIs in 1161 at bats. This clearly shows that Arenado has been better at home than on the road, but is it due to the high altitude or are there other factors causing these varied home/road splits?
Well, Arenado has a career BABIP of .305 at home and .277 on the road. BABIP (batting average on balls in play) is affected mainly by three factors: defense, luck, and talent level. If a hitter faces excellent defence, they get less hits, lowering their BABIP. If a hitter is lucky, they get more hits off of bloop singles, dribblers, or other hits with weak contact, increasing their BABIP. And if they are just a very skilled hitter, they make more hard contact, leading to more hits and a higher BABIP.
Arenado is a very skilled hitter who makes a lot of hard contact, but because of the reduced air resistance, he is able to hit the ball even harder. This is why his BABIP is higher at home than on the road and why his career average is 42 points higher at home than on the road.
If you look at D.J. LeMahieu’s career numbers, you will see the same trend. His career slash line at Coors Field is .329/.387/.451, and his slash line on the road (this does take into account some road games in his first year when he played for the Cubs) is .264/.312/.339. And just like Arenado, he has a considerably higher BABIP at home (.381) than on the road (.313). That higher BABIP, which is caused by reduced air resistance, has led to a higher career batting average at home than on the road.
Although it is clear that playing home games in Coors Field results in better offensive statistics, determining by how much is difficult. Let’s look at former Rockies catcher Nick Hundley. Here are his home/away splits for 2015 and 2016 if he played 162 games both at Coors and on the road.
(Baseball-reference.com)
As you can see, Hundley was significantly better at home in 2015, but in 2016, was much better on the road. I haven’t investigated Hundley enough to give a definitive answer as to why that is, but this is a common trend for Rockies hitters. One season they play better at home and the next they play better on the road. Here are Nolan Arenado’s home/road splits for the 2017 season as of 5/30:
(Baseball-reference.com)
Now these splits are very similar, but they show that the Coors Field Effect is inconsistent and unpredictable. Nolan Arenado, whose career splits definitely show inflated home statistics, is hitting better on the road this season than at home. And this is despite the fact that his BABIP is higher at home than on the road, which means that he may still be hitting the ball harder at Coors Field. Again, I don’t know why Arenado’s splits are reversed this season, but it shows that not every player is affected by the high altitude the same way all of the time.
You can look at every Rockies hitter and you will find some that hit better at home, some that hit better on the road, and some that hit the same on the road as at home. But it is hard to come to a conclusion just off of individual stats. Pointing out individual trends doesn’t really tell us a lot about the Coors Field Effect as a whole, just how it affects each player. To better understand the general impact of the mile-high altitude, I researched the 2016 Rockies home/road splits as a team. Here is how the team fared as a whole at home versus on the road:
(Baseball-reference.com)
These splits clearly show a large difference between hitting at Coors Field and hitting elsewhere. Although most teams— and players— will hit better at home than on the road, the difference is not as large as the one presented in the table above. The Rockies hit 58 points better and slugged 118 points better at home than on the road.
And as you can see, their BABIP was significantly higher at home than on the road. Their BABIP on the road was right around where you would expect a typical team to be, but their BABIP at home was impressively high. If a hitter had a BABIP around .345 for a whole season they would be one of the best contact hitters in the MLB. Daniel Murphy, who was second in the MLB with a .347 average, had a BABIP of .348 last season. For a whole team to have a BABIP of .348, there has to be another factor besides for talent level responsible for the elevated BABIP. For the Rockies, it is the mile-high altitude.
But most players, and teams, hit better at home than on the road, so I decided to look at how the Los Angeles Dodgers, a team in the same division as the Rockies, hit at home and in Colorado. Last season, the Dodgers hit .249 as a team (the league average was .255), and since they play in the same division as the Rockies, they had a slightly larger sample size compared to other MLB teams. Here are their splits at home (81 games) and at Coors Field (9 games) last season:
(Baseball-refence.com)
As a team, the Dodgers were much better at home than at Coors Field. In fact, their hitting statistics at Coors were significantly lower than their average hitting statistics throughout the whole season. There are a lot of potential reasons for the decline in production from Dodgers hitters at Coors Field, but the point of this article is not to determine why some hitters and teams are less successful than others at Coors Field. It’s to show you that it is hard to make conclusions on the effect of the high altitude and reduced air resistance in Colorado.
Due to the fact that some hitters and teams do not show elevated stats as a result of playing at Coors Field, I find it hard to always assume that a hitter or a team would have lower stats if they didn’t play in Colorado. Last season, if Nolan Arenado played for a team other than the Rockies, he would still have been an All-Star and one of the best hitters in the league, but he may not have won the Silver Slugger Award. However, it is very difficult to determine what his stats may have been if he played for another team. This season, Arenado is hitting better on the road, so you cannot say that he relies on the high altitude for his impressive hitting stats.
This is not to say that Rockies hitters don’t benefit from the high altitude, just that making conclusions about the kind of player they would be without it is hard because one season their home/road splits may be totally unequal, but the next they may be reversed. It is important to understand that there is an advantage to hitting in Coors Field, but it is not consistently reflected in a hitter’s performance.