So I’ve begun to think about some tables for TTL and as of right now I’m leaning toward showing everything per plate appearance (or at bat/ball in play when appropriate). Now for hitting stats this is how it’s done and it makes perfect sense. However for pitching stats, rate stats tend to be per inning or per 9 innings (ERA, WHIP, K/9, HR/9, etc.). Now it doesn’t make intuitive sense to talk about “earned runs per plate appearance,” but for everything else I don’t know why we still don’t use the same denominators as when looking from a hitter’s perspective.
For instance, this year Carlos Marmol is certainly having an outstanding season, striking batters out at nearly 16 per 9 innings (which would be a record). However, while much more than half of his outs are coming via the K, he has truck out 41.1% of the batters he has faced. This is slightly ahead of the 38.5% posted by Billy Wagner this season and trails the 44.8% posted by Eric Gagne in his 2003 season and the 42.5% posted by Brad Lidge in 2004. No doubt Marmol is having a very good season, but the choice of denominator here is what really counts. Excluding walks and especially hits from the equation doesn’t really make much sense in this case; why should the fact that a ground ball sneaks through the hole rather than become an out make a difference on how successful a pitcher is at striking guys out?
Therefore, what I’ve decided to do is display parallel stats for hitters and pitchers. These will typically be on a per plate appearance/at bat/ball in play basis, although I do want to show one of ERA/FIP/xFIP for pitchers and RC/27 for hitters (again to be parallel). Not only does this the process easier by keeping the same fields for both groups, to me it makes sense as the way we should be looking at stats. Hitters try to score runs, pitchers try to prevent runs; hitters try to get on base and pitchers try to make outs; hitters try to help their team win and pitchers do the same. Since it’s two sides of the same coin, why do we currently treat them differently in so many cases, even when looking at “advanced” metrics?