THE BOOK--Playing The Percentages In Baseball

Monday, February 08, 2010

How do you spot a lefty masher?

Pat asks:

However, lefty/right analysis has advanced since my adolescence, and I think this post from MGL is a must read for what I’m talking about. In it he says:

IOW, how a batter does against RH pitchers informs us on how he will likely do against LH pitchers and vice versa. Why? Because there is not much of a spread in true platoon splits among ML baseball players yet there is a large spread in overall true hitting talent among ML baseball players. So if we see a large platoon split, like for a player like [Ryan] Howard, it is likely a fluke. If a player does really well versus RH pitchers but terrible against LH pitchers, both the “really well” and the “terrible” numbers are likely fluky and the “truth” is somewhere in between.

Howard has a .719 OPS in the last 4 years versus LHP. How would we estimate his “true” OPS versus LHP? You might be tempted to just use the .719, which is not too good or you might be tempted to use the .719 and then regress that toward the league average for a LH batter of Howard’s physical characteristics, which might be around the same or a little higher – I don’t know. Both of these methods would be wrong. You cannot ignore the fact that he also hit 1.052 in OPS versus RHP over the same time period (last 4 years) and in many more PA. This suggests that he is a very good hitter overall (which he is) and that the .719 is somewhat of a fluke.

And then Pat asks the interesting question: do splits change by age?

I’d also like to see how players do split wise over the course of a career. Obviously the skill of hitters diminishes over time, but it’d be interesting to see if the splits are larger. Ryan Howard certainly is not “old” at 30 years old, but his skill set and physical size certainly have shifted over the years. While he was never slender, Howard is certainly a “bigger” guy than he used to be, and probably a good amount slower. Besides that, as players get older they tend to lose some hand-eye skill, an effect that may be magnified when facing a pitcher of the same handedness. Here are Howard’s wRC+ from 2006-2009, going from overall to versus lefties and then versus righties.

2006: 166, 133, 182
2007: 140, 110, 159
2008: 123, 91, 143
2009: 141, 71, 178