Pitch Sequencing Trends in the Statcast Era

As the Statcast era continues to age, we baseball obsessives are collecting more and more pitches to analyze in countless different ways. MLB Advanced Media releases 90 different metrics for every pitch thrown, including a pitch’s classification, where all the defenders are standing upon the pitch being thrown, exit speed, launch and spray angle, etc. Analysts across the web, armed with this exhaustive data set, have been able to unearth previously unknowable mysteries regarding team and player performance and league-wide trends.

One area of pitching analysis that has been largely untouched by the public is pitch sequencing. Baseball Savant has done some work with visualizing how a pitcher sequences his pitches, but to my knowledge there is no way to look at pitch sequencing for the league as a whole and see which sequences are most used and most effective. I was curious how pitchers have attacked hitters since 2015 (the beginning of the aforementioned Statcast era), so I parsed through every pitch thrown in the regular season starting from the beginning of the 2015 campaign up until August 11th of this year. I looked at how pitchers have paired pitches during every plate appearance. I discarded pitches that were not thrown to the same batter or the same inning; a pitch that is thrown to end an inning followed by a pitch to start an inning should not be considered a sequence (same can be said for two different plate appearances). The sequences should be read as the pitch on the right precedes the pitch on the left. Now, let us look at the trends: