Messing With Park Factors

Last night, for reasons I still don't know, my mind wandered while driving home from a friend's apartment towards baseball and park factors. I've always wondered why we only use a players home park as the park factor by which to adjust his offensive or pitching performance. After all, baseball teams spend half of their season on the road so it would stand to reason that one would look at both a home and road park factor, no?

In the absence of actually sleeping, I decided to goof around in Excel for a bit, as I'm known to do. I took the 2B/3B and HR park factors from StatCorner, and decided to perform a lazy-man's park adjustment to Miguel Cabrera's 2013 season. I should note that I used only park factors for right-handed hitters as Cabrera is a right-handed hitter so there's no need for me to worry about how Miami's Taxpayers Dicked Over stadium treats LHB's.


What I did was take Cabrera's game logs from Baseball Reference and then looked up the park factors for each of the road parks he played in. I then took a simple average -- though weighting each road PF by plate appearances I suppose would be the best thing to do but I'm just a fool with a computer and procrastinating sleep -- of his road park factors. For Miguel Cabrera, the road parks he played in had an average 2B/3B PF of 102 and 96 for home runs. For context, Comerica sits at 117 for 2B/3B and 92 for home runs. If you wanted, you could weight the park factors. Approximately 52% of his PA's came on the road, so if we weight his 2B/3B and HR park factors for that, we'd get 109 and 94.

Then I broke up his total stats into home/road numbers and adjusted the road doubles, triples and homers. Then I did the same for his home statistics which I then added to his road numbers to get an adjusted number of doubles, triples and home runs. This seems like it's probably the wrong thing to do, but as I said earlier, this is just one lazy man's way at attacking a wandering thought.

The result of this was Cabrera loses a couple doubles, has the same number of triples and gains about three home runs. This gives him a park-adjusted wOBA of 0.464 which is up from his raw wOBA of 0.455 at Fangraphs. Converting that to runs puts Cabrera's experimental park adjusted wRAA around 76-77 runs or 4-5 runs more than what his listed wRAA is on Fangraphs.

Now, I want to do one more example, so let's go with Alex Avila since I have his Baseball Reference page currently open. Avila's road 2B/3B PF for left-handed hitters is 103 and the road HR PF is 97. At home they are 103 and 110. Adjusting his doubles, triples and homers doesn't do much as Avila basically gains fractions of hits. This gives Avila a park-adjusted wOBA of 0.308 which is actually slightly less than the raw wOBA of 0.310 at Fangraphs. As such, his adjusted wRAA comes out at -1.9 runs which is close to his -1.2 at Fangraphs.

My take away from this is that maybe road PF's don't matter that much, or that I just didn't use them well enough. Or, perhaps, they matter simply for hitters in the NL West where the parks vary from hitter havens (Colorado, Arizona) to pitcher parks (San Diego, San Francisco), I'm not entirely sure. For now, however, my curiosity is mostly satiated.