The Colorado Rockies are coming off one of the best seasons in their history. They reached the postseason for the first time since 2009 and a big part of that was their success on the road. The club finished the 2017 season with a 41-40 road record, tied with the 2009 club for the best in franchise history. A 41-40 record on the road is a solid mark, but it’s also not something one would expect to be a franchise’s best over a 25-year span. Difficulty playing on the road is unlikely to go away in 2018.
In fact, since the Rockies came into existence in 1993, there have been 209 individual team seasons with a road win percentage higher than the .506 of a 41-40 record. That means, on average, every other team in the league has had 7.2 individual seasons with a better road record than the best road record the Rockies have produced during that same time frame. As the Rockies prepare to open the season on the road against the Arizona Diamondbacks, let’s dig into why they’ve historically struggled so much away from the friendly confines of Mile High Stadium and Coors Field.
Since 1993, the Rockies’ overall road win percentage of .395 is the worst in the Majors. They’re also worst in several offensive categories such as runs per game, on-base percentage, and slugging percentage. That, obviously, is not great, but it’s also no secret that the Rockies have had their share of struggles over the years. Maybe they simply just haven’t been good. Do we see the same thing with regards to their home record? As it turns out, we don’t. At home, the Rockies’ win percentage of .543 ranks 13th in the league and is close to the league’s overall home win percentage of .538.
The Rockies’ disparity of 148 points in win percentage home and road is by far the largest in the league. It’s 44 points larger than the next largest individual team’s gap and nearly double the league average. Over a 25-year sample, it’s nearly impossible to explain away a gap that large by random variance. A far more likely explanation is the Rockies have either a competitive advantage at home or a competitive disadvantage on the road.
In 2014 Matt Gross delved into this using the Rockies’ large gap in wRC+ at home and on the road. It’s an outstanding piece, but also leaves open the potential that wRC+ may just not be accounting for Coors Field properly, thus explaining the apparent disparity in production home and road. Let’s examine the same thing with a different metric—one that wasn’t available at the time of the aforementioned article—to try to get a clearer answer.
Expected weighted on-base average (xwOBA) uses a batter or pitcher’s exit velocity and launch angle, combined with actual walks and strikeouts, to give us what that player’s weighted on-base average (wOBA) should have been when ballpark, luck, and defense are stripped from the equation. We can also break these numbers down by team and use each team’s home-road splits to see if we find a similar story here.
One downside of a stat like xwOBA is, being a relatively new metric, we have just three seasons worth of data. In those three seasons, Rockies hitters have an xwOBA of .321 at Coors Field. This ties them for 12th in the league and is slightly better than the league average home xwOBA of .317. On the road, however, xwOBA for Rockies hitters nosedives all the way down to .290. This is 29th in the league, well below the league average road xwOBA of .309.
Following a continuing trend, this gap of 31 points in xwOBA home and road is the largest in the league. This essentially means that no team has had a greater difference in terms of quality of contact, walks, and strikeouts between their home and road games than the Rockies have. Something certainly seems to be awry, but we should also look at the pitching side of things before we come to any conclusions.
Perhaps, in spite of the intention to take ballpark out of the equation, xwOBA has missed the fact that it’s just flat out easier to make quality contact at Coors Field, thus artificially inflating home xwOBA numbers for the Rockies. If that’s the case, we should expect to see something similar from Rockies pitchers, with their home xwOBA allowed being higher than it is on the road.
Since 2015, Rockies pitchers have allowed an xwOBA of .318 in home games. This ties them for 22nd in the league and is above the league average of .309. Perhaps we’re onto something here. On the road, however, Rockies pitchers’ xwOBA actually increases by five points to .323. It does bump them up a few spots to a tie for 19th, but their home-road xwOBA differential is tied for 16th in the league—squarely in the middle of the pack. We aren’t seeing the same extreme difference here, making it unlikely the large difference on offense is merely a quirk of Coors Field not being properly accounted for.
The data presented here seemingly leaves us with two potential explanations:
1. Throughout their history, the Rockies have been one of the worst offensive teams in the league, but their home field has provided a larger advantage than most, allowing them to look better than they’ve actually been.
2. Throughout their history, the Rockies have been roughly an average team on offense, but a competitive disadvantage on the road has made them appear worse than they’ve actually been.
Both of these explanations are plausible. After all, someone has to have the worst offense. What makes option number one less likely is not the fact the Rockies have had the worst road offense in the league overall; it’s the consistency with which they’ve put up poor offensive numbers on the road.
In an average 25-year sample, one would expect to see some good seasons, some bad seasons, and some that were roughly average to match the natural ebbs and flows that occur during a time frame that large. This is what we see with the Rockies road offense:
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In their 25-year history, the Rockies have managed exactly one season in which they placed in the top half of the league in runs scored on the road. In that season, they barely made it, coming in 14th out of 30. In 23 out of 25 years, they’ve come in 20th or worse and on a whopping seven different occasions they’ve come in dead last. This is not a normal distribution of outcomes and suggests something is going on that’s hindering the Rockies’ ability to put runs on the board when they leave their home ballpark.
The cause of these road struggles remains mostly a mystery. One theory is that, with pitches moving differently at Coors Field than they do elsewhere, it wreaks havoc on Rockies hitters constantly having to adjust to pitches moving more than they’re used to when they go out on the road. Perhaps it’s more difficult for Rockies players to sleep on the road as they come down to sea level after being at altitude. Whatever the cause, the effect seems rather clear and it probably isn’t going away anytime soon.
The only thing that has been a constant throughout the team’s history is that they’ve struggled on the road. If a major piece of solving a problem involves knowing that it’s there, maybe the Rockies are finally in a position to defy history and do better than barely above .500 on the road. But as the Rockies begin their 26th season of play tonight, on the road, remember that the trouble is neither a philosophical flaw of the team nor a character flaw of the players. It’s built in to the DNA of baseball at altitude.