Sliders are a heavy platoon pitch. The traditional pitcher will use the slider when they have the platoon advantage and go to the changeup when they do not. The numbers make it clear that this is the best approach (it is also a big reason why pitchers who throw mostly sinkers/sliders don't succeed very often as a starter). However, a discussion between Eno Sarris, Dave Cameron, and Marc from USSMariner prompted me to look at pitchers who move or don't move their slider based on platoon. That is, do some pitchers who still like to throw their sliders without the platoon advantage throw it in a different location on average?
So I looked at pitchers that have at least 100 sliders (MLBAM tags) this season (I am only looking at 2013 data) against each lefties and righties. 100 is admittedly an arbitrary number, but it is few enough to include relievers, but hopefully enough that we get pitchers who actually it as a weapon against both lefties and righties. This gives us 60 pitchers, so here are their average locations against lefties, followed by righties, and then the standard deviation of both their average vertical and horizontal locations to give us an idea of how big the difference is. The following is the results, sorted by pitchers with the largest horizontal difference, meaning the ones who moved it the most by platoon.
Some surprises and some non surprises here. Bronson Arroyo being near the top is no surprise considering all of the weird things he does while pitching, and it wasn't surprising to me that a guy like Matt Moore was near the bottom. Several Yankees rate highly, which is interesting. Hughes and Phelps are homegrown, but Kuroda and Kelley are not, so it is hard to say that it is taught (though perhaps it is something they look for). The three Japanese natives rate highly, which I don't find all that surprising considering the difference in slider compared to the traditional North/South America slider. Ryu is right about in the middle interestingly (though he has a pretty traditional changeup he uses against righties).
Madison Bumgarner and C.C. Sabathia don't rate well, though their sliders are sometimes considered cutters. I thought it was interesting that Ervin Santana and Bud Norris didn't rate well even though they are starters that notoriously heavily rely on the slider. Yovani Gallardo's slider usage was recently called into question despite the lack of platoon splits, and I think we see why his platoon splits are not large. He locates the slider away no matter the platoon.
Some other notables include Alexi Ogando, who doesn't have a real sweeping slider, but has always used it frequently. His doesn't really change in location, and I thought Luke Gregerson, who reportedly has at least 3 sliders, would be closer to the top than he was.
I was surprised by how much difference there was on average, especially considering what we saw with the average whiff location charts. I guess it would stand to reason that pitchers who are more willing to throw the slider to both lefties and righties would have their sliders in different locations (or have slightly different sliders) by platoon. The horizontal difference was much more prevalent than the vertical difference, with some pitchers (such as Sale, Richards, and Miller) having no difference in vertical location of the slider.