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How Does the DH Affect National League Pitchers? (2020 Fantasy Baseball)

Jul 18, 2020

One of the many drastic changes to the 2020 MLB season is the presence of the universal designated hitter. National League pitchers have long had the luxury of facing a completely useless hitter a few times a game. In 2020, those pitchers will be replaced by hitters who actually know what they’re doing a little bit with the bat.

The question that needs to be answered now is what kind of difference will this make on pitching statistics? While the truth will only be revealed after the season plays out, we can get a pretty good idea of what’s likely to happen by looking at data from past years.

Let’s get into some analysis and try to glean some fantasy-relevant conclusions.

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Overall Comparison, Last 10 Years

The most rudimentary way to get an idea of the difference in pitching in the American League vs. the National League is to just look at the raw ERA, WHIP, and strikeout numbers. Let’s have a look.

National League pitchers clearly have an easier time in terms of preventing runs, as NL pitchers have posted a lower ERA than AL pitchers in each of the last ten seasons.

That’s not quite the same story with WHIP, with the AL beating the NL in the category in 2015, 2016, and 2017.

Strikeouts have been steadily on the rise for both leagues, but the National League has stayed a step ahead of the American League even through that – posting a higher K/9 as a league in each year since 2013.

When we aggregate these ten seasons together, we get this:

AL ERA, Last 10 Years: 4.16
NL Era, Last 10 Years: 3.99

AL WHIP, Last 10 Years: 1.32
NL WHIP, Last 10 Years: 1.31

AL K/9, Last 10 Years: 7.79
NL K/9, Last 10 Years: 7.96

Pitchers vs. DH, Hitting Stats

I thought it would be interesting to see what kind of stats the positions have put up as a whole over the last five seasons. I went back through each box and added up the stats for each position. Here’s what it looks like:

Breaking news: designated hitters are much better than pitchers at hitting.

How Much of an Effect will the Change Have?

It’s impossible to say exactly, but it will likely have less of one than you might suspect. Pitchers only accounted for 5% of total plate appearances in National League hosted games last year. The average plate appearances a pitcher gets in a single game is 2.1 (the average for all other positions is 4.1-4.2, besides catcher, which comes in at 3.8).

From the above, we can see that the AL and NL ERAs are typically separated by about 0.2 runs over a full year. Let’s do some more rough math now that we see the DH and pitcher stats above.

Over the last ten seasons, we see about 2.2 hits per earned run recorded. Last year, a National League pitcher that was healthy all year faced an average of 50 pitchers. Taking that 50 and multiplying by the average pitcher batting average gives us about six hits (50 * .126). If we replace those 50 pitchers with the league average DH’s .251 batting average, we get 13 hits. That’s a difference of seven hits, which would roughly equate to three extra earned runs.

Let’s take a pretty league average season and see how those three runs change the ERA figure. If a pitcher throws 180 innings and gives up 80 earned runs, that is an ERA of 4.00. Adding three earned runs to the mix raises the ERA to 4.15. That is about the same difference that we see above.

Let’s apply this math to the new 60-game season look. If a pitcher makes 12 starts, he would face about 25 pitchers total without the DH. Those pitchers would generate about three hits in that example. A DH would generate six hits in 25 plate appearances on average. Three extra hits equate to 1.5 extra earned runs.

Taking a 66 inning, 29 earned run season to a 66 inning, 30.5 earned run season inflates an ERA from 3.95 to 4.16 – a difference of 0.2.

The best guess as to how much ERAs will rise for National League pitchers that no longer get to face the pitcher is around 0.2 runs — not a major difference, but not insignificant, either. It’s enough to flip some National League pitchers below American League pitchers in rankings, but no major adjustments to anybody’s expectations should be made.

Strikeout Rate Analysis

Possibly a bigger advantage that National League pitchers had over American League pitchers is the strikeouts they can rack up against their counterparts. To test this, I looped through every pitcher with at least 500 plate appearances against them last season (roughly 80 innings or so) and checked to see much of their K% came from pitching against other pitchers.

For example, National League Cy Young winner Jacob deGrom faced 804 batters last year and struck out 255 of them. Of these 804 batters, 54 of them were pitchers, and he racked up 35 strikeouts against those 54 pitchers.

What I wondered from there was about how many of those 35 strikeouts would he have gotten if those 54 pitcher plate appearances were designated hitters instead. I decided to just apply deGrom’s season strikeout rate (32%) to those 54 plate appearances, giving him a hypothetical total of 17 (54 * .32) strikeouts in the 54 plate appearances.

This is just to say, “if deGrom struck out pitchers at the same rate as he struck out everyone else, what would his season strikeout have been?” The answer in deGrom’s case is 29.4%, a difference of 2.2%. This actually turned out to be one of the higher differentials.

Here are the leaders:

The average differential was just 1.3%, again — nothing huge, but not insignificant.

Conclusion

A fair adjustment to make to National League starting pitcher projections would be to inflate all of their projected ERAs by 0.2 runs and to lower their projected strikeout rates by 1.3%. This will not dramatically alter your SP rankings, but it absolutely should lead to some minor adjustments, with some American League pitchers leap-frogging some National League arms.

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Jon Anderson is a featured writer at FantasyPros. For more from Jon, check out his archive and follow him @JonPgh.

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