All About Pitcher Perceived Velocity

On Sunday, I read the following comment on Rotoworld about Chase Burns‘ start:

His fastball was located well, but, as has been true in his first two starts, he doesn’t get tons of whiffs on the pitch. He had eight whiffs on 55 total fastballs in this one, with a whopping 16 foul balls. His fastball has below average extension and simply isn’t as elite of a pitch against big league hitters who can handle high velocity.

Sure enough, his four-seamer has generated just a 7.6% SwStk% despite the pitch averaging a scintillating 98.2 MPH. So it got me thinking about perceived velocity, which extension affects. If a pitcher is throwing 95 MPH, but the batter perceives the pitch’s velocity to actually be 97 MPH, or perhaps 93 MPH, that should matter, right? I would therefore think the gap between perceived and actual velocity would influence the pitch’s whiff rate and the pitcher’s strikeout rate. So I decided to dive in and find out if that theory is true.

I looked back to all pitcher seasons since 2021 and pulled the pitcher’s most used fastball, between the four-seamer (FF), sinker (SI), and cutter (FC). I arbitrarily filtered out fewer than 300 pitches in a season, as I’m not sure how quickly this metric stabilizes and wanted to reduce noise. I then calculated the difference between perceived and actual velocity and ran correlations between that number and whiff/swing for the pitch and strikeout rate. Let’s check out the results.

These aren’t super high correlations. However, they are clearly meaningful and makes it seem pretty definitive that the gap between perceived and actual velocity does matter and can affect whiff and strikeout rate.

What’s interesting here is how much more correlated the difference for cutters is. Perhaps that’s just a small pitcher season sample size issue, or maybe something more. It’s also interesting to find that the gap correlates with strikeout more than whiff/swing% across all pitch types. I wouldn’t have expected that given that whiff/swing% relates to that specific pitch only, while strikeout rate is driven by the pitcher’s entire repertoire.

So where does Burns rank here? Well, he was filtered out since he has only thrown 122 four-seamers, but has averaged 98.2 MPH with his fastball, with a perceived velocity of…98.3 MPH. His 6.4 feet of extension is just below the league average of 6.5 feet. Between the nearly identical perceived to actual velocity and near league average extension, I’m not sure I would chalk up the underwhelming SwStk% on the pitch to his extension. There must be something else going on, but that’s for a different day.

So who are the leaders in perceived velocity over actual velocity this year?

There’s a real mix of pitchers here, from starters to relievers, aces to not aces. Let’s discuss some.

It’s been a rough year for Bailey Ober despite ranking third on this list. His strikeout rate is way down, while his actual four-seam velocity sits at a career low. Luckily, his perceived velocity makes it appear much faster than it actually is, which is essentially when he’s barely averaging over 90 MPH with the pitch. Though he’ll probably improve from here, he’s not someone I would go out and target, unless of course I see a velocity rebound.

Zack Wheeler has posted a 33.6% strikeout rate this year?! Holy guacamole. That’s a career best…at age 35. He already throws hard and aside from his peak in 2019-2021 where he hovered around 97 MPH, he hasn’t lost any velocity. Throw in the additional 1.5 MPH of perceived velocity and you get an ace.

Bailey Falter is another interesting cat in the Ober mold, in that his velocity is below average, though not nearly as much as Ober’s, so the boosted perceived velocity should be a boon. But…it hasn’t been. His strikeout rate has continued its slide, down a fourth straight year and the fastball earns a below average rate of whiffs. Even with career best velocity and the perceived velocity boost, if he can’t even muster a 20% strikeout rate, I’m not sure if there’s a reason to be optimistic. For owners trotting him out there each week because of his shiny 3.69 ERA, that won’t last as his .238 BABIP reverts toward league average.

Jake Irvin has lost significant velocity this year, so the extra oomph from his perceived velocity is vital to his success. It hasn’t been enough though to prevent his strikeout rate from tumbling. Give me a middle reliever in an NL-Only league instead.

Pablo López first enjoyed a velocity boost in 2023, and he’s maintained it since. He gets even more benefit thanks to the perceived velocity, though his strikeout rate has moved in the wrong direction since peaking the same year of that initial velocity spike. We’ll see how his velocity holds up after returning from injury.

David Peterson had at one time shown a nice mix of skills, with strikeouts and groundballs and the hope his control wouldn’t get too much in the way. Now, his strikeout rate has collapsed the past two seasons, all the while his walk rate has improved marginally. His SwStk% is at its lowest as well, which makes one think the season has been a disaster. From an ERA perspective, it hasn’t. But he has also benefited from great fortune as his much higher SIERA and xERA attests. I wouldn’t automatically be starting him each week in mixed leagues.

Not only has Cristopher Sánchez recorded the best velocity of his career, but his perceived velocity makes that sinker appear even faster! It has all led to the season we dreamed of when we first heard his velocity was up during spring training. He now owns a drool-worthy skill set of strikeouts, walk avoidance, and grounders.

Adrian Houser, where did you come from?! Who expected a 1.60 ERA from a White Sox starter after eight starts? Houser’s sinker velocity is up this year, though merely back in line with where it was from 2022 and earlier, as it dipped the past two seasons. Obviously, his 1.60 ERA is a complete mirage, so he’s going to be a risky start in AL-Only leagues as the implosion inevitably comes.

Did you realize that Tylor Megill owns a 29.2% strikeout rate?! Me either. It has mostly been driven by a jump in called strike rate, so it probably won’t last. We’ll also have to see how he recovers from the elbow injury he suffered that landed him on the IL currently.

I was cautiously optimistic about Chris Paddack coming out of spring training where he showed increased velocity, but that wasn’t sustained, as he’s pretty much in line with last year and below his 2019-2021 years. The perceived velocity helps, though, but instead he’s posted a career worst strikeout rate and SwStk%, with a microscopic CSW%. He had gone on a lucky run earlier in the season, but that luck is gone now and he should be nowhere near rosters.

Now let’s flip over to the pitchers with perceived velocity most below their actual marks.

This group of names is far less interesting, which shouldn’t be too surprising.

I’m pretty shocked to find Luis Castillo’s name atop this list. His velocity has consistently declined since peaking in 2020, so the fact his perceived is significantly lower would normally be a huge red flag. And indeed, his strikeout rate has plummeted to a career low of just 20.2%. Yet, his 3.31 ERA is better than his career average, as he has posted the lowest HR/FB rate of his career and highest LOB% since his 2017 debut. He has massively overperformed both his SIERA and xERA, which make him an ideal trade candidate given his name value.

I’m also surprised to see Framber Valdez’s name here since he hasn’t shown any effects of reduced perceived velocity. His strikeout rate is right in line with past years and everything else looks normal here. Heck, his ERA and SIERA are basically identical to last year! Nothing to worry about here, move along.

In his move to the rotation from the bullpen, Clay Holmes had already lost a whopping 3.1 MPH on his sinker, so another mile per hour loss in perceived velocity feels like a disaster. Sure enough, his strikeout rate has sunk below 20%, while his SwStk% is in single digits, so it’s clear his stuff is just nowhere near the same as it was as a reliever. Luckily, he has benefited from the combo of a suppressed BABIP and inflated LOB%, so he has dramatically overperformed both his SIERA and xERA. Given that, the low strikeout rate, and the big innings increase, he seems like another ideal trade candidate if you own him.

Perhaps this lack of perceived velocity is why Jesús Luzardo has consistently recorded below average Stuff+ marks on the pitch, despite averaging in the mid-90s. This year, his velocity is actually at the second highest mark of his career, rebounding from last year’s trough. His strikeout rate has rebounded along with it, so he hasn’t outwardly been affected by the poor perceived velocity. What’s really killing him is the .381 BABIP, which has pushed his ERA well above both his SIERA and xERA. Unlike two of the above names, he actually makes for a strong buy low target.