Pittsburgh Pirates pitchers can now point to some real results when hitters’ eye levels are changed
In my last article we took a look a more theoretical look at how Pittsburgh Pirates pitchers can maximize their likelihood of a successful batter faced in any single at bat. We aimed to determine if the ages-old pitching practice of “changing eye levels” by mixing vertical pitch locations on a hitter is truly effective.The recommendation from that article was that greater changes in eye level change, up to 10.4 inches, maximized a pitcher’s likelihood of a stifling a hitter.
That is, however, a very specified view on the issue, as it only looks at specific at bats and not what a season long trend should look like. To understand this with more nuance we’ll be taking a look at season long, individual Pittsburgh Pirates pitching performances and finding where the trend is.
The first place to look is how eye level change relates to ERA. First, here’s a graph of ERA versus eye level change for every pitcher who threw more than 20 innings in 2017 with Pittsburgh Pirates starting pitchers highlighted:
And here is the same graph for 2017, only with the Pittsburgh Pirates’ relievers that will be around for 2018 highlighted:
What’s interesting about this graph is that there is a slight arch to the trend line, meaning that at either lower or higher amounts of eye level change, ERAs are generally lower, but having an average eye level change, of about 8 inches, means a pitcher is more likely to have higher ERA.
There are a few reasons this might be, but I think the most compelling hypothesis is that pitchers with large amounts of variation are able to generate a lot of strikeouts and weak contact, so they have a lower ERA, and Pitchers with less variation tend to not walk as many batters, so they have lowered ERAs, but the middle zone doesn’t generate enough eye level change to affect outcomes, but has too much variation to avoid the walks.
If we look at the starters’ graph, of the five starters who pitched most of the season Chad Kuhl was right in that no-mans-land of about 8 inches, and also had the highest walk rate of the bunch. Conversely, on the relievers’ graph, Felipe Rivero had the lowest average eye level change of anyone on the Pirates staff, but was able to command his pitches well, and in combination with truly nasty stuff, was able to have a very low ERA.
For pitchers like Kuhl and Daniel Hudson, sitting in that no-man’s-land negatively impacts their pitching performance; moving towards either more control with fewer walks, or increasing their pitch height variation to increase successful batters faced, will help them to improve. However, both of these pitchers had trouble with the walk last year, so perhaps moving toward less variation would be better.
What about FIP though?
The graphs for FIP can be interpreted similarly:
If we look toward slightly more advanced metrics, we can see some other interesting stuff.
Starting with Strikeouts per 9 innings we get this:
This relationship is essentially linear, meaning more variation in eye level results in more strikeouts. Specifically, this means that increasing a pitcher’s eye level change by about one additional inch results in roughly 0.5 more strikeouts per 9 innings pitched on average.
Perhaps the most interesting part of this graph has to do with former Pittsburgh Pirates number one prospect Tyler Glasnow.
Glasnow’s strikeout rate is almost exactly what we should expect based on his vertical location changes, given his proximity to the red trend line. Just based on this, Glasnow ought to be a really effective pitcher, and clearly has the tools to be one but that has obviously not panned out. More on that after the next set of graphs.
Since we’ve just looked at strikeouts, let’s take a look at walk rates while we’re at it:
The takeaway from this graph is similar to what I said earlier in the article, as pitchers increase their change in vertical location, the less control they seem to have, and the more walks they give up.
Getting back to Glasnow specifically, you can see that he is way above the trend line for his walk rate. Why is that?
If we look at the average vertical location of Glasnow’s pitches, they are just 6 inches from the bottom of the strike zone. The average strike zone he faced was almost 22.5 inches. This means that Glasnow had about 16 inches of strike zone that he wasn’t attacking frequently.
The average location being so low in the zone is a trademark of a pitcher looking to generate weak contact. With Glasnow’s larger amount of vertical change and a location so low in the zone, it’s not surprising that he walked so many batters; he’s essentially walking a tightrope along the bottom edge of the strike zone and it’s unnecessary.
Rather than trying to change Glasnow’s whole approach, the Pittsburgh Pirates ought to let him creep a little higher in the zone, and work a ton of strikeouts with the nasty curve and scorching fastball. I’ve written on this subject before, but it bears repeating, the Pirates should really let their “stuff” pitchers go for strikeouts.
Switching gears a bit, for those of you who read my last article I showed a graph that looks like this:
I said that the Pirates should look to have a staff with an average eye level change of about 7.8-8+ inches to see a quick improvement to their pitching staff; however as I said before in this article, that 8 inch mark is “no-man’s-land” when it comes to ERA. So what would this pitching staff look like?
For starters, pitchers like Rivero, Nova, and Williams, who have all had success with relatively little vertical variation should stick with it. Guys like Kuhl and Hudson, who have had trouble with the walk, would likely be better off reducing their variation to closer to the likes of Rivero and company.
In the case of a pitcher like Glasnow, changing variation is not the issue, but rather the problem is the areas he’s attacking. Allowing him to go after batters rather than making him pitch to contact will almost certainly lead to major league success for him and the Pirates.
All this averages out to a team eye level change closer to that 8 inch mark, that would put the Pirates back into post-season contention.
Making a decision on which pitchers should do what for their usage of eye level change has a lot to do with the characteristics of the pitcher themselves. Making these changes, however, will likely have a very positive impact on the Pittsburgh Pirates pitching staff, exploiting an advantage that can return the staff to the dominance of the 2015 team.