Introduction

In 2014, Matt (RIRF) wrote ‘the’ epic Purple Row article on the Coors Hangover. He made a few key points:

• The Rockies consistently have a huge wRC+ home/road splits. From 2002-2014, they were 17 points worse on the road, despite the stat being park adjusted. It is normal for teams to hit better at home – other NL teams were also better at home. But other NL teams hit only marginally better at home, varying from 4 to 9 points.
• Matt made a convincing case that the Rockies were an average hitting team at home between 2002-2014. Thus, the split was primarily caused by the fact that the Rockies were awful on the road – dramatically more awful than other NL teams.
• Matt ascribed this difference to the ‘Coors Hangover’ – basically, Rockies hitters have to make an enormous adjustment to how the ball moves when going from Home-to-Away.

My Approach

I looked at the same data as Matt, but starting close to when he left off and running to 2018. I present data here in graphical form instead of as a table. For each season, I looked at each NL team’s home and away wRC+. 2018 is below. As you'd expect, teams generally hit better at home (the blue line) than they did away (red line).

2018 NL wRC+ splits

If you average 2013-2018, teams hit better at home

The graph below shows each team’s average home and road wRC+ for 2013-2018. Good teams during this era generally hit well (Dodgers, Cards, Nats, and Pirates). Bad teams hit badly (Padres & Phils). Almost everyone hit a good bit better at home. The Rockies hit OK at home … and atrociously on the road. This is consistent with Matt’s findings for 2002-2014.

Average NL wRC+ Splits, 2013-2018

The Rockies are again an outlier

The graph below shows the difference in home and away wRC+ for each team (blue minus red in the graph above). [Thanks to ESterps for suggesting I make this a bar chart.] As already stated, teams usually hit better at home and so most points are near the average of ~8. There are 2 exceptions:

• The Rockies hit 20 park-adjusted points better at home, similar to the 17 point gap Matt found for 2002-2014.
• The Mets actually hit worse at home! For what it is worth, Matt also found that the Mets were near the bottom of the league in this difference, though they were close to everyone else and certainly not worse at home! Maybe the Mets just get tired of planes flying overhead. Or maybe, LOLMets is the only explanation. Poor Mets.

Difference in Home and Road wRC+, 2013-2018

In summary, everything that Matt found from 2002-2014 is still true through 2018. It would be great to do more but I've struggled to get home/road splits of the data. It would be great if we could:

• Look at Rockies’ success against specific pitches at home vs on the road. I suspect that certain pitches are easier to hit at home and certain pitches are nearly impossible for Rockies to figure out just after leaving altitude. Unfortunately, while it is possible to see how Rockies hitters do against different pitches, FanGraphs does not allow you to compare home/away splits against specific pitches. Does another source have this data? I would bet a good chunk of change that other NL front offices have this information close at hand.
• Do this same analysis with DRC+. Does Baseball Prospectus allow you to get home/road splits for DRC+? If so, I can’t find it.

Editor's Note: This FanPost was originally published on February 20, 2019. The timestamp has been updated.