How Much is an Extra Mile Per Hour on Your Fastball Worth?

Hope springs eternal at the start of the season. Players who have spent the winter improving themselves finally get to showcase their gains. For many position players, that often comes with proclamations that they're in "the best shape of his life.” Sometimes that is true for pitchers, but more common in recent years is “he went to Driveline” (or a similar place).

For the hurlers, those winter visits to the private science-of-baseball labs might result in new or refined pitches in their arsenal. They also might result in the always-coveted increase in velocity.

For the Twins this spring, starting pitchers Bailey Ober and Simeon Woods-Richardson and reliever Jorge Alcalá garnered attention with their newly augmented fastball velocity. Before that, it was Griffin Jax and Joe Ryan.

While it remains to be seen if those gains will translate into regular season impact, they offer reasons to believe that the players might have another gear than they previously showed. Woods-Richardson’s velocity increase has been present in his first two starts in Triple-A, and Ober was a full tick above last year’s average in his first start, despite struggling mightily. Alcalá’s bump has come north, too, averaging 96.6 mph in his first few relief appearances.

We believe that more velocity leads to better results, but is that true? What is that worth in practice? Does increased fastball velocity result in better run prevention? Is a velocity uptick more impactful for some hurlers than others? Let’s see if we can find out.

Getting Grounded
Velocity is increasing throughout MLB, and has been for a while. The league-average four-seamer in 2008, when pitch tracking was implemented, was 91.9 mph. Last season, it was 94.2 mph. That increase has been driven less by increasing maximum velocity (no one has topped Aroldis Chapman’s 105.8 mph from 2010), than by an increasing number of pitchers throwing hard. 

Sixty-four different hurlers touched 100 mph or better last season, per Statcast, and 38.0% of all four-seamers thrown were harder than 95 mph (more than double the same figure for 2008). The upper limit isn’t going up, but things are getting more crowded near it.

With the help of Statcast search, I binned every four-seam fastball and sinker thrown over the last 3 seasons (2021-2023, more than 1,000,000 of them combined) into one-mile-per-hour increments. The average Major League four-seamer in that period was 93.9 mph and allowed a .256/.345/.447 triple-slash line and a .344 weighted on-base average (wOBA). Sinkers have averaged 93.2 mph, while getting hit to .283/.360/.424 and a .344 wOBA.

The two dominant fastball types at the league level have allowed the same production, albeit with different shapes. Four-seamers suppress batting average and on-base percentage better than sinkers, but are more susceptible to slugging. That makes sense intuitively — sinkers tend to generate ground balls, which can sneak through infields for singles, boosting batting average and on-base percentage; and four-seamers tend to generate flyballs that are either caught for outs or go for extra bases, suppressing average and increasing slugging.

Around those averages, the distribution of velocity of those pitch types at the league level looks like this:

About 60% of the four-seamers thrown in the last three seasons have been between 92 and 96 miles per hour. Sinkers are just a tick lower on the velocity scale, as you can see above, and about 55% of those have fallen between 91 and 95 miles per hour.