As part of exploring Dustin Ackley's "lefty strike" problem, I dug into where exactly pitches are called strikes and balls to left-handers. I'm still working on how to chart it in a illustrative manner, but for the time being, this old chart is still close to how things have been called the past three years. That right-most chart should actually be left-handed batters, not right-handed as listed. It's a little difficult to tell, but interestingly, the strike zone widths are very similar. It's just that for right-handers, the zone tends to be equally wide on either side of home plate. For lefties though, it's close to the plate on the inside half, but extends a whopping five inches off to the outside.
Unrelated to that, I noticed how Michael Saunders was swinging much more often this season at pitches within the strike zone and only a little more often at pitches outside it. Here was the table that I compiled from StatCorner where zoneSw is the percentage of pitches, within the strike zone, that Saunders swung at and where oZoneSw is the same but for pitches outside the strike zone.
Since then, I've made some progress on mapping out the limits (based on when pitches cross the 50% called ball/strike barrier) of the practical strike zone and I applied that to StatCorner and re-ran everyone's strike zone/plate discipline numbers. So now, when you look at Michael Saunders' page, the zSw% represents the percentage of pitches in the lefty strike zone that are swung at and not just in the platonic, theoretical strike zone.
With these updated, more accurate, rates, look now at how Michael Saunders has changed this season.
The league average has been steady for the past four seasons at 58% in zone and 28% out of zone.
Before I issued a qualified endorsement of Saunders' new approach, noting that
Saunders is swinging more at pitches outside the zone, but not many more. And his swinging rate on pitches inside the strike zone has gone way up. That's generally good.
With this more targeted look at the strike zone that Saunders and other left-handed hitters have to deal with, I can now more forcefully note that this is a direct improvement on his part. The swing rate on pitches not likely to be called strikes has actually gone down a little and is slightly less than the Major League average now.
Meanwhile, the difference in how often he has swung at pitches within the called lefty zone has increased by a large rate and is blowing away the league average. Again, of course it matters what Saunders can do with those swings but there's little to doubt here that he has become much more aggressive only within the confines of the strike zone.