What fastball velocity does Spencer Strider need to have to be successful?

Atlanta's strikeout king is currently working with diminished stuff; how successful can he be with it?

“It’s got to be better […] Not acceptable for me.”

Those were the words of Spencer Strider just minutes after Atlanta’s 5-3 loss to the Washington Nationals on Tuesday night. He allowed four runs on six hits across 4.2 innings, taking the loss in his first game back from the injured list after a hamstring strain took him out of commission for almost a full month.

One of the biggest areas of concern for many Braves fans was Strider’s fastball velocity - the flamethrower, who averaged 97.2 mph on his Cy Young finalist season of 2023, was sitting at just 95 on Tuesday night and was lower than that for several innings.

And Strider’s gone on the record in the past about his fastball velocity and how it’s necessary for his whole ‘thing’ to work. “There are very few right-handed starters that average over 98 with a low VAA,” Strider told Eno Sarris of The Athletic. “It’s just hard to hit. The harder you throw, the less time they have to decide so it’s even harder to hit.”

While Strider has added a curveball and still has the changeup, they’re ancillary options at best to his primary whiff pitches of the fastball and slider. “When I throw my fastball and slider, I expect a miss. That’s what I want, that’s my goal, that’s what the pitches are supposed to do,” he told Sarris.

With lower velocity, how effective can Strider be?

Let’s talk about it.

The slower fastball is more hittable

I mean, duh? But let’s quantify it. To Statcast!

I ran a few searches here. The first is to look at the batting average and wOBA against his fastball (over his entire career) on a variety of different speeds: 97 and up, as well as everything 95 and under.

≥ 97: .207 BA, .264 wOBA
≤ 95: .364 BA, .441 wOBA

I think with Spencer Strider, it’s important to discuss that his velocity number is a bit understated from the perceived velocity. With his exceptional extension - how close he releases the ball to the plate - the velocity is perceived as hitters as even higher than it reads on the gun. With his 90th-ish percentile extension, he picks up around one to 1.5 mph of ‘perceived velocity’ over the actual velocity.

Now, some caveats: Strider’s a bit unlucky with those softer fastballs - the xBA is .299 and xwOBA is .388, but still - that’s a stark difference off of two mph.

But we can do more.

It makes sense that he gets more whiffs off of faster fastballs, but how much more? Heaters of ≤ 95 have a whiff rate of 20%, but when he’s at his usual velocity? 29.5%.

But believe it or not, we can go even deeper.

The slider is impacted by the lower velocity

This one’s a bit harder to search directly via Statcast, but I think I’ve figured out a workaround.

When Strider’s averaging 97 or harder on his fastball, the whiff rate on his slider is 55.3%. When he’s averaging 95 or lower, like this season, the slider’s whiff rate is ‘only’ 47.6%.

The problem is quantifying the arsenal interaction - is it getting less whiff because of the lower velocity of the fastball, or is it getting less whiff because of the lower velocity of the slider itself?

(Strider’s slider is down just under two miles per hour from 2023’s 85.6 mph average velocity, sitting at 83.9 mph this year.)

I don’t think we’ll ever completely know, but I did try and figure it out.

The average slider of 86 mph or harder, across all MLB starters, has a whiff of 34.2%. Below 84 mph? 29.7%.¹

I also pulled the accumulated Stuff+ numbers for both 2023 and 2025, in an attempt to quantify the quality of Strider’s accumulated pitch mix. In 2023, he had a 126 Stuff+, but just a 100 Stuff+ this year.

In essence, his arsenal was 26% better than the average pitcher’s arsenal in 2023, but it’s roughly league average this year.

Gulp.

Strider with league average stuff isn’t that special, honestly, a fact that he sort of acknowledged after the Tuesday start. “The stuff wasn’t consistent. […] If I can’t be better, I don’t need to be out there.”

The good news is that many people around the team seem to believe that Strider’s going to get there with more starts. “The more he throws, the better he’s going to get.” said manager Brian Snitker after the start. “We have to start somewhere. As long as he’s healthy, does his sides and makes his next start on Sunday, it’s going to continue to get better. The more pitches, the sharper everything is going to get.”

Strider agreed with Snit’s assessment. “It takes time.”

He expounded on what has to be done, admitting that he needs to get more biomechanical information to determine where to make his improvements. “(The work) leans heavily on technology, No. 1. I think otherwise it’s hard to have a direction. You want to make sure you’re evaluating yourself honestly. That’s something that technology helps you do. It’s not going to b.s. you. I’m pretty well aware of some things I need to improve upon from a (body) movement standpoint. Trying to use stuff to help track the progress and direct the work. Then the specific methods and drills, things like that, come as a result of the evaluation and analysis.”

One of the improvements needs to be his control.

Reminder: Control is the ability to throw the ball in the strike zone, while command is the ability to locate the pitch where you want it, in or out of the strike zone.

In the fully healthy seasons of his career, Strider was hovering around 51 to 52% in the zone overall. This year, across two starts? 47%. Doesn’t seem like much, but it definitely reflects in Strider getting behind in the count. So far this season, he’s gotten a first pitch strike in 57.5% of plate appearances on the season. In 2023? 67.1%.²

So, to recap: The fastball’s close to two mph softer than 2023, leading to 10% less whiffs, more balls being thrown overall, and a significant reduction in his Stuff+ to exactly league average.

Can Strider be successful at this velocity?

I think he can, but with some caveats.

He’ll be good, but not great. Think an ERA in the mid-3.00s to maybe even a 4.00. And he’ll need to change how he does it - rather than sitting at 90% FB/SL, he’ll need to add the changeup and curveball more.³

But Strider’s aware of the extra work required, and appears to be up to the challenge. “It takes time. It’s not like one day everything magically got better for everybody. That came from deliberate work.”

And if Strider’s shown anything in his career, it’s that he’s willing to put in the work.

1. Now obviously this isn’t perfect, because a larger percentage of the >85 mph sliders are thrown by very good pitchers, but it’s the best I can do here.

2. His overall strike percentage is down only 4%, but it’s significantly more egregious on the first pitch and impacting the entire at-bat.

3. For the record, he was 78% FB/SL in the Nationals start, throwing the changeup 13% and the curveball 9%.