That is exactly correct. I wrote about that over 5 years ago. There is almost no spread in true talent platoon splits among RHB. Therefore any large platoon split you see for a RHB is almost certainly a fluke, even over a large number of PA.

Ken, I regressed his platoon ratio too much. According to The Book, for 750 PA, you regress about 57%, not 80%. That would put his true OPS versus LHB at .791 and not .805, not a gigantic difference.

You also have the issue of how much to weight each year, which I don’t know. I typically don’t do any weighting at all for platoon splits, but that is probably incorrect, as you want to do some weighting if you think that the underlying talent can change over time. In Howard’s case, of course, his platoon ratio has been getting larger. So if do any weighting, his estimated true OPS versus LHP would get worse, maybe in the .775 range. Of course if you do weighting, you have to reduce your effective sample size as well, and then regress more.

I think that he will improve over time against lefties as he becomes a better hitter – but that doesn’t mean that his past performance has been based on luck or that we should expect him to substantially improve on his performance this year.

thanks for stopping by and clearing this up. I have always been in the platoon Howard camp, but this makes a lot of sense.

First we’ll estimate his overall true OPS. In his career, it is .966. We’ll regress that and call it .930, which is a typical projection for him. Now we have to take his observed platoon ratio (I like to use ratio – some people use a differential) and regress that. His observed platoon ratio for those 4 years is 1.052/.719, or 1.46. For the average lefty, it is 1.20 and we just don’t see that much variation among players in their true platoon splits. IOW, that 1.46 is likely very (but not completely) flukey. We might regress that 1.46 80% toward the league average of 1.20, to get 1.25. That is Howard’s “true” estimated platoon split.

Now we simply apply that to his overall estimated true OPS of .930 and the fact that he faced 62% RHP. That gives us an OPS of .805 versus LHP and 1.006 versus RHP.

So .805 is an estimate of his true OPS versus LHP.

Nick, I’m not trying to f***k with you. I am trying to illustrate why the idea that Howard is terrible (or not much more than an average hitter) against lefty pitchers and should be platooned, as some analysis have even said, is (likely) nonsense.

As Paul has shown, how can two lefty hitters with the same playing time and the same exact numbers versus LHP have such different estimates of their true talent versus lefty pitchers? The both hit .300 (wOBA) against lefty pitchers, but one batter computes to a projected .376 versus lefty pitchers and the other computes to .300! How can that be?

Because how a batter does overall (versus lefties and righties) tells us more than just how he does against LH or RH pitchers alone, even if we want to estimate how they will do in the future against either lefties or righties alone.

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 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 Howard, it is likely a fluke. So 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 .741 OPS in the last 3 years versus LHP. How would be estimate his “true” OPS versus LHP? You might be tempted to just use the .741, which is not too good (not terrible of course) or you might be tempted to use the .741 and then regress that toward the league average for a LH batter of Howard’s physical characteristics, which might be around the same – I don’t know. Both of these methods would be wrong. You cannot ignore the fact that he also hit 1.042 in OPS versus RHP over the same time period (last 3 years) and in many more PA. This suggests that he is a very good hitter overall (which he is) and that the .741 is somewhat of a fluke. The fact that it is only in around 750 PA, the equivalent of a little over a year of full time play against all pitchers, makes it very reasonable that it could be flukey. We see flukey results in one season of play all the time. Heck, one standard deviation due to chance in 750 PA is around 30 points of OPS.

Anyway, do what would be the correct method for estimating Howard’s true OPS versus LH pitchers using his last 3 years of stats? Basically the same as Paul did above.

First we’ll estimate his overall true OPS. In his career, it is .966. We’ll regress that and call it .930, which is a typical projection for him. Now we have to take his observed platoon ratio (I like to use ratio – some people use a differential) and regress that. His observed platoon ratio for those 3 years is 1.042/.714, or 1.406. For the average lefty, it is 1.20 and we just don’t see that much variation among players in their true platoon splits. IOW, that 1.406 is likely very (but not completely) flukey. We might regress that 1.406 80% toward the league average of 1.20, to get 1.24. That is Howard’s “true” estimated platoon split.

Now we simply apply that to his overall estimated true OPS of .930 and the fact that he faced 62% RHP. That gives us an OPS of .810 versus LHP and 1.004 versus RHP.

.810 is a far cry from .741

So if we are going to talk about how Howard is likely to do versus LHP, let’s at least get our numbers right. .810 is higher than Werth and Jeter versus RHP. We don’t talk about how terrible Jeter and Werth are versus RHP, which they face most of the time, do we?