Why Do MLB Pitchers Focus So Much On Fastball Velocity?

Image credit: Mason Miller (Photo by Eddie Kelly / ProLook Photos)

There seems to be a never-ending discussion among baseball fans that can be divided into two groups: Those who note how pitchers keep throwing harder and harder and those who decry the never-ending push for more velocity.

The first group’s argument can be summarized as follows: Velocity is vitally important, and pitchers who want to have MLB success are wise to push to throw as hard as they can.

And the second group’s argument: The never-ending chase for velocity is likely to blame for the ever-increasing rate of arm injuries, something that wasn’t as much of an issue when pitchers didn’t throw as hard.

Both sides have some valid points, and the argument isn’t going away any time soon. The charts we’ve compiled below may help to explain why the chase for velocity isn’t likely to disappear, even if it may increase injury risks.

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Specifically, we’re using the excellent Baseball Savant tool to look at how MLB hitters have fared against four-seam fastballs divided into different velocity buckets so far in 2024. What we’re not looking at is how well each pitch is located, what the count was or how well the pitch moved. We’re only separating these pitches out by velocity.

As you may note below, the harder an MLB pitcher throws, the more effective his four-seam fastball is. It’s a relatively linear relationship. Overall, MLB hitters are hitting .244/.311/.401 with a 25.1% whiff rate this year, and the average velocity of a four-seam fastball is 94.2 mph. Hitters like to see fastballs, so against those four-seamers, MLB hitters are slashing better: .246/.334/.424 with a 21.7% whiff rate.

If a pitcher throws at or below the league-average four-seam fastball velocity, on average, they are giving up above-average production on those four-seamers. If they throw 95+ mph (which is above MLB average velocity), they are giving up below-average production on four-seam fastballs. And if they throw 100+ mph, hitters dread seeing their fastball.

Major League Four-Seam Data

Velocity range	AVG	obp	slg	ops	whiff rate
89-90 mph	.290	.369	.539	.908	15.3
91-92 mph	.267	.344	.487	.831	17.9
93-94 mph	.250	.344	.438	.782	21.2
95-96 mph	.241	.328	.411	.739	23.8
97-98 mph	.209	.293	.336	.629	25.4
99-100 mph	.184	.282	.267	.549	29.1
101-102 mph	.143	.236	.214	.450	36.6

We can do the same for Triple-A pitchers’ four-seam fastballs in 2024.

Once again, we see a similar relationship: If you throw harder, you have more success. The only difference is we didn’t include 101-102 mph fastballs for Triple-A, as there have been less than a hundred thrown all season (pitchers who throw 102 mph don’t hang out in Triple-A very long). As one might expect, there was a much more statistically-robust total of 435 fastballs thrown at 101-102 mph for the major leagues.

Triple-A Four-Seam Data

Velocity Range	AVG	OBP	SLUG	OPS	whiff rate
89-90 mph	.310	.417	.547	.964	17.6
91-92 mph	.281	.398	.481	.879	21.1
93-94 mph	.272	.393	.453	.846	23.7
95-96 mph	.250	.365	.414	.779	25.7
97-98 mph	.232	.364	.355	.719	29.2
99-100 mph	.168	.289	.211	.500	34.2

Again, this is only four-seam fastballs. But what if we looked at how hard pitchers threw their slider? We’re again not focused on how the pitches move, so we’re looking at all types of sliders: traditional, sweepers, gyro and all else.

In case that leads you another question, here’s the same breakdown for four-seam fastballs from MLB in 2009. MLB hitters showed similar degradations in production and increases in whiff rates as velocity climbed, and similar production against each fastball velocity bucket. But in 2009, only 6% of four-seam fastballs were 97+ mph. Now 17% of them are 97+ mph, so there are a lot more at-bats taking place in the higher ranges of these buckets.

2009 Velocity Range	AVG	OBP	SLG	OPS	Whiff Rate
89-90	.297	.387	.515	.902	13.6
91-92	.290	.380	.488	.868	14.8
93-94	.274	.363	.446	.809	17
95-96	.243	.328	.387	.715	19.3
97-98	.238	.316	.361	.677	20.8
99-100	.189	.268	.292	.560	26.3
101-102	.118	.250	.118	.368	30.6

Major League Slider Data

Velocity Range	AVG	OBP	SLG	OPS	whiff rate
81-82 mph	.221	.271	.399	.670	31.3
83-84 mph	.218	.265	.383	.648	33.4
85-86 mph	.215	.267	.362	.629	32.7
87-88 mph	.228	.278	.371	.649	34.5
89-90 mph	.219	.281	.361	.642	36.7
91-92 mph	.164	.236	.240	.476	37.6

The results aren’t as linear as the fastball velocity buckets, but other than 85-86 mph pitches having better results than 87-88 mph, there still is a definite improvement in results as velocity increases and swing-and-miss rates climb.

With changeups, however, there is no clear relationship between velocity and success. Changeups rely on movement, deception and in many cases, a velocity separation from a pitcher’s fastball. So, a pitcher who throws a hard changeup that lacks deception may not be benefiting from that velocity.

As you can see below, by not controlling for anything other than velocity, there does not seem to be any significant relationship between changeup velocity and the pitch’s effectiveness.

Major League Changeup Data

Velocity Range	AVG	OPB	SLG	OPS	WHIFF RATE
79-80 mph	.239	.287	.405	.692	32.4
81-82 mph	.221	.265	.365	.630	30.9
83-84 mph	.238	.284	.405	.689	31.3
85-86 mph	.233	.275	.368	.643	32.1
87-88 mph	.231	.275	.374	.649	31.1
89-90 mph	.210	.252	.320	.572	31.1
91-92 mph	.229	.282	.328	.610	30.2

So what does it all mean?

Throwing harder, especially when it comes to fastballs, leads to more success for MLB pitchers. If you throw harder, hitters have less time to react, and that makes a hitters’ job tougher. It sounds simple, because it is.

But it’s a simple truth that many baseball fans seem to struggle to accept.