2020 From Both Sides: Pitching and Batting

Last week, I wrote about the 2020 MLB season and how it was different from previous (in other words, full-length) seasons of 162 games, and uncovered that while absolute batting numbers were logically about one-third of what we saw in a typical year, that overall trend lines were not very different.

This week, I wanted to take a look at pitching to see how the trend holds. Like for batting statistics, to qualify for statistical awards (like ERA or winning percentage), pitchers need to have a minimum amount of play to qualify. For batters, this is 3.1 plate appearances per scheduled game; for pitchers, this is one inning per scheduled game. So for a typical year, to qualify for one of these titles, a pitcher needs to have a minimum 162 innings pitched, but for 2020 the minimum to qualify was 60 IP.

The scatterplot below relates innings pitched to ERA+ (a normalized ERA correcting for variability across different stadiums.) As with the batters, the short schedule is clearly visible as the light blue trend line around 60 IP. Looking at the slopes of the lines, the slope for 2020 is less than half that of 2017, and about one-fourth that of 2018 and 2019. Also, about 20 percent fewer pitchers qualified for postseason ERA or win percentage awards as in a typical year. So across a smaller number of innings pitched, there was more variability in 2020 in ERA+.

Relating ERA+ to strikeout/walk ratio also suggests that while there was greater variability in ERA+ (correcting for the lower number of innings for all pitchers), 2020 statistics were not shockingly different from previous years.

As a fan, it's comforting to know that, as hard as it was to not be able to go to games, to witness a regular season that was only about a third as long as a typical one, and playoffs held at neutral sites, we can still look to the 2020 season as having outstanding achievements in the offensive and defensive dimensions of the game. Now we can look forward to a full season, and as vaccination numbers increase, being able to go to games in person.

Please take a look at these visualizations in Tableau Public, where you can interact with them. You can isolate specific years and highlight individual players. (Batters are here, and pitchers are here.) I have also been making more card paintings so look for some additions to the galleries soon.