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Do walks hurt more now?

With home run rates breaking records in 2017, I wondered if pitchers with high walk rates were more prone to bad ERAs than in the past. Should we avoid high-walk pitchers even more now?

National League Wild Card Game - Colorado Rockies v Arizona Diamondbacks Photo by Christian Petersen/Getty Images

Today’s post is the result of something that has been bouncing around in my head all season with all of the home run spikes we’ve seen in recent years. There’s no doubt that home runs are at an all time high right now. Starting with that truth, I reasoned that pitchers that allow more walks should be hurt more by the increasing percentage of runs coming via the home run. I mean, they should, right?

If no one is on base, it is just a solo home run. But if you’ve walked one or two batters, now you’ve allowed two or three runs on one swing. And sure, a double can drive home multiple runs as well, but the runners have to be in the right spots to take advantage. On home runs, the runner on first has no problem scoring. This seems like a logical theory.

So, now that the season is over, I can finally investigate this question: are pitchers with walk rates worse than league average more prone to high ERAs now than they were in the recent past? Are walk-heavy starters more risky than they were before?

A warning: there be graphs, stats, tables, and some math ahead. I promise it won’t scar you permanently. I’ll try to keep it short and to the point.

I pulled walk rates and ERAs for all starters with 100 innings or more in each (they didn’t have to reach that mark in all of them, just one season at a time) of these seasons: 2014, 2015, 2016, and 2017. I then just plotted ERA vs walk rate (BB%) for each season.

Following are the graphs for each of the four seasons:

First, if you are familiar with correlation coefficients (R squared), these are very low. Generally, you want to be around one. The closer to zero you are, the weaker the correlation between the two variables, in general. Real baseball data is noisy and pitchers can have very low ERAs despite many walks by carrying a very low BABIP or just not having the walks hurt them as much as they should. These guys create variability in the data and there are enough of them that all of these R squared values are poor.

That being said, you can compare the R squared values for the different years and see that 2014 had by far the strongest correlation of the four years. That flies in the face of my hypothesis that home run rates lead to more danger for high-walk pitchers. Similarly, the slope of the best fit line tells us how strong the relationship between ERA and BB% is for each season. Again, 2014 has the highest slope.

So, the linear regression analysis (all the stuff I just described) points to no added walk penalty in the new home run era. I decided to be thorough and look at it in a different way as well.

I took the average ERA of all pitchers in a given season with walk rates worse than the league average from that year. Then, I divided that by the league average ERA for that season. This normalizes the numbers for changes in league-wide trends involving ERA/run scoring.

Here’s a handy table that summarizes all of the results so far:

So, once again it appears that pitchers with bad walk rates in 2014 were more hurt by it than those in subsequent years. What does this all mean? It means my initial hypothesis appears to be wrong. Even if it has some logic behind it, the data does not support the idea that pitchers with walk rates worse than league average will be more prone to bad ERAs in 2017 (or 2018) than they were in previous years.

So, don’t be afraid to draft starters with bad walk rates but high strikeout rates or ground ball rates (see: Ray, Robbie). They aren’t any riskier now than they have been before. They are still a big risk for a high ERA, but it has nothing to do with all the balls flying out of ballparks now. It’s just because, you know, baserunners lead to runs and you kind of want to limit them. Some food for thought for your 2018 preparations. Tschus!