Coors Field Hangover

October 20, 2008

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As many of you know, I have been trying to determine if the Rockies have a significantly different LD rate at home vs. road. To me, this would indicate a Coors Hangover with breaking balls (they would break more sharply on the road, and the Rockies would need to adjust for that after seeing flat breaking balls at home).

I found what I needed in’s PI section. I took the raw data and massaged it to force it to give up its secrets.

Here is the data. Strikeouts, bunts, and fielder’s choices are excluded from the rates. There were only 8 FC all year, so they are statistically insignificant. Bunts were excluded because the hitter is not trying put good wood on the ball. Since I only included at bats, sac flies are not included (they are PAs, but not ABs)

Without further ado:

5557 total at bats.
4270 full swing BIP
Ground: 1861 – 43.6%
Fly – 1499 – 35.1%
Line: 910 – 21.3%

2153 full swing BIP
Ground: 906 – 42.1%
Fly – 751 – 34.9%
Line – 496 – 23%

2117 full swing BIP
Ground: 955 – 45.1%
Fly: 748 – 35.3%
Line: 414 – 19.6%

3.4% more balls in play are hit for line drive in Coors than on the Road. Line drive are very commonly hits (I haven’t calculated BA for the various types yet) so the extra LDs are going to boost BA and slugging.

Also, Rockies hitters struck out 651 times on the road vs. 549 on the road. It seems logical that this is due to more sharply breaking moving pitches, although there might be other explanations.

The extra 100 BIP at home (due to the fewer Ks) would result in 30 extra hits (assuming a BABIP of .300) – or an extra 0.4 hits/game.

I have not run the numbers for any other teams, so I’m not sure if this is a typical home/road split of not. I’ll probably run the numbers for the rest of the NL West to get a decent baseline.

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