Fastball Velocity Detection: Looking Back

Last week I wrote about how tracking fastball velocity increases may allow fantasy managers to decide when to sit/start/stream starting pitchers (try saying that three times fast…). Seeking to take research done by others and make it fantasy actionable, I analyzed baseball savant batted ball data to find the pitchers who have steadily increased their fastball velocity, four-seamers in this case, in their most recent outings. You can do this by simply going to a player page and using our pitch info velocity graphs to visualize velocity trends. But you would have to already have pitchers in mind and then go to their pages to check in on their velocities. In my case, I’m analyzing larger datasets and flagging pitchers who have continued to increase game average fastball velocity in three or four games. I provided a table of starting pitchers who were flagged prior to June 16th in last week’s post. Now, let’s check-in and see how these pitchers did in their first outing following my analysis:

Let’s segment out these performances with a real sophisticated classification system called, “Gem, Decent, and Stinker”:

Gem, GSV2 above 60: Taijuan Walker, Sandy Alcantara, Ian Anderson, Nick Pivetta, Shohei Ohtani, Josiah Gray.

Taijuan Walker threw a real gem with only one hit, one walk, and nine strikeouts. While his fastball velocity did not continue to increase in this most recent start, he had something going that led to a great performance. We can’t expect fastball velocity to just increase all season long. But Walker’s post-analysis performance is a good example of a pitcher showing signs of a hot streak.

Decent, GSV2 between 45 and 60: Miles Mikolas, Jon Gray, Joan Adon.

Jon Gray may be falling into a weird category here. My guess is that he is still ramping up from injury and getting into a rhythm on the season. It was certainly a decent start and I’m liking what I’m seeing from him lately.

Stinker, GSV2 below 40: Taylor Hearn, Patrick Corbin, Germán Márquez,

Four-seam fastball velocity increase isn’t everything. These pitchers are perfect examples of how a larger picture is necessary to determine whether or not they would be a good fantasy add. While a few of these pitchers showcased some promise or sign of improving, home runs, hits, and walks brought them down into the stinker category.

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I’m still working on improving the flow of the python code I use to detect possible hot streak pitchers using four-seam fastball velocity, but once I have it “production-ready” I’m happy to share. Here is a fresh list of qualified pitchers who have gained a few ticks on four-seam fastball velocity (as compared to their in-season average) and may be worth taking a closer look at before their next start: