We looked at ballpark factors last week, and discussed how wOBA and other rate stats can vary by virtue of the park they were generated in. At the end of the post, I left you waiting with bated breath for the reason behind the big OPS+ discrepancy between Evan Longoria and Adrian Beltre.
The short answer? I was more or less right.
Fangraphs’ wRC+ is based on wOBA, while B-R’s OPS+ is based on OBP and SLG. My first question was whether the discrepancy could be in the way OPS weights (or doesn’t weight) its components, where wOBA does.
But the problem doesn’t seem to lie in the fundamental components of the number. Beltre’s OPS is .892 and Longoria’s is .850. Not terribly different, and Beltre’s is still higher than Longoria’s. So somewhere in the application of league averages and park factors, the two are flipped, and Longoria comes out with a 10% lead.
The only thing I could think of that would give Longoria such an advantage was an extreme ballpark factor, which makes sense since the two play in parks at complete opposite ends of the spectrum. We also know that B-R uses single-season park factors, which can vary more than multi-year factors.
B-R publishes park factors for each team on its page. I wasn’t able to find a list of Fangraphs’ park factors by year, but I did find something else interesting. Take a look at the page for the 2011 Texas Rangers. It lists both multi-year and single-season park factors.
The Rangers’ multi-year park factors for batting and pitching are 111 and 109, respectively. Above 100 indicates a hitter-friendly park. The single-season numbers are 117 for batters and 115 for pitchers. That’s a pretty significant discrepancy – nearly half again as far from average as the multi-year factors.
The Rays, on the other hand, remain relatively consistent. Their multi-year batting/pitching factors are 92/91 respectively, with single-year factors of 92/92.
I think we’ve spotted our discrepancy. Fangraphs’ multi-year park factors gave both Longoria and Beltre a wRC+ of 134. We can expect that when calculated over multiple years, B-R’s and Fangraphs’ park factors probably converge.