The humidor has been in place since the 2002 season. Because the Rockies went to the World Series in 2007, the humidor has been locked in as one reason for the Rockies success. I can't argue that pitching wins championships. The humidor helps pitching (?). My question then is whether the humidor has removed the unique brand of baseball that Coors Field provides and in its creation has it done more harm then good?
In the last two seasons the Rockies have fallen to 38 and 35 wins respectively at home. Previous to this, the Rockies had a distinct advantage at Coors Field, with only three losing seasons since its inception in 1995. Watching opposing teams visit Coors over the last couple of years, it seems the fear of the place is gone. No longer do teams come in with a defeated look. Oftentimes they come in and light the place up with their pitcher's leaving with no scars. Has the humidor given the opposition hope and meanwhile handcuffed our own team?
First off let's discuss park factors. Baseball at altitude has always been a boom for batter's and a nemesis for pitchers. For the gory details about park factors, see here. Below is how Coors Field has played since its opening in 1995. Before the humidor (1995 - 2001), the average park factor was 124, and after its installation it dropped to 114. Essentially a 10% decrease in offensive output with the humidor. Specifically run scoring decreased by about 1.3 runs per game which equates to about 100 less runs by either team. Pretty spectacular but wait…2012 numbers look awfully close to pre-humidor levels. Could the humidor be just a mirage?
From 2007-2010, Rockies had by far their greatest talent of starter's in their twenty year history. The graph below shows starting pitching winning percentage in four year increments. The high point below, 2007 - 2010, when Rockies starter's compiled a 236-210 (.529 winning percentage). The green line below this shows four year averages of the pitching park factors. The dip in the park factor would suggest that decent Rockies pitching might have played a bigger role in taming of Coors Field then the humidor.
But wait the humidor helped our pitchers by reducing home runs and thus the winning percentage above is just further proof that we are truly entering a pitching renaissance at Coors Field. For the final word on pitching performance I have graphed FIP (Field Independent Pitching stats) for Rockies pitchers both home and away. The blue points are home and the green points are away. Starting with the humidor, FIP values become more consistent. But in that same time period of 2007 - 2010, we see a drastic road decrease in FIP indicating we had a better overall pitching staff then in the past. When Rockies pitching became average again in 2011 and 2012 we start to see home and road FIP start to diverge again, indicating that pitching is more of a factor.
Of course pitching park factors also consider opposing pitching staffs. This is where I think the humidor has really affected our Rockies. For the pitching park factors to decrease like this then either opposing pitchers have figured out Coors Field or our own offense has been hampered Graph below shows the run scoring rate at Coors Field for our offense. Pre-humidor Rockies average 7.1 runs per game and since then this has fallen to 5.8. Rockies offense has always been difficult to judge because of playing half their games in a great run scoring park. Hard to imagine the talent of the Blake Street Bombers days was that much greater than our current talent. One has to wonder if there is more of a mirage in offensive prowess because of Coors Field.
In conclusion I think the humidor overall affect is limited. I don't think it makes bad pitching better. Rockies during their playoff run 2007-2010, had assembled its best pitching staff ever to grace the mound in Colorado. This staff conquered Coors Field by pitching well and this could be seen at Coors Field and on the road. The last two years would suggest that Rockies staff, regardless of the humidor, is not very good. If in fact it is good pitching rather than the humidor that makes the difference then shut down the humidor and take back the offensive advantage at home. Winning formula then is to score seven runs a game, batter opposing teams staffs, win 50 games a year at home, and make Coors Field an advantage.