What Royce Lewis and Byron Buxton's Big Losses of Swing Speed Tell Us—and Don't Tell Us

[Lucas Seehafer PT]

Two of the Twins' biggest stars saw their swing speeds decrease in 2024. That's a big deal, but it might be fixable—and it might be telling us something else.

Image courtesy of © Jesse Johnson-Imagn Images

Baseball Savant began publishing swing data during the 2024 season. As such, we now have access to impactful metrics such as swing speed, swing length, and the solidity of contact for the second half of 2023 and all of last season, right at our fingertips.

Savant defines swing speed as the average velocity of the sweet spot of the bat during the top 90% of an athlete’s swings. They locate the sweet spot 6 inches from the top of the bat, and lop off that bottom decile of swings on the hunch that they're “non-competitive” attempts, such as check swings and bunts, which would artificially lower the average swing speed. There are two properties of physics that are important for understanding why an athlete’s swing speed is important: momentum and torque.

Momentum (often labeled as ‘p’) is simply the product of an object’s mass and velocity (p = mv). Essentially, an object will possess more momentum the faster it is moving, given its mass remains unchanged. This is true of a baseball bat; its mass does not change during a swing (assuming it doesn’t break), and therefore, a faster swing has more momentum than a slower one.

Torque (‘t’) is the force produced by an object as it rotates around a given point. As such, we can tweak Newton’s linear first law of motion (force is the product of mass and acceleration; F=ma) a bit to torque is the product of an object’s moment of inertia and angular acceleration (t=Iα). Moment of inertia can be expressed as the product of an object’s mass and the square of the radius of the circle about which it is rotating (I=mr2) and the rate at which that rotation is occurring (therefore, t=mr2α). (Note: I can already hear some of you physics types clacking away at the keyboard: “This is much too simplistic! A baseball bat isn’t a simple pendulum!” yada yada yada. Whatever, this simplistic version is good enough to get the point across.) [Editor's note: I can already hear some of you non-physics types cackling bitterly at the idea that what we just read is the simplistic version. Don't worry, Lucas is going to land this plane for us.]

What this means in English: Generally speaking, a faster swing will exert greater torque and momentum on the ball, and that will result in the ball registering a higher exit velocity. And we know that a harder-hit ball will more frequently result in a better outcome (i.e. home run, double, fielding error, etc.). 

Additionally, these physics principles tell us that an athlete can improve their swing speed in two ways; they can rotate more quickly to accelerate the bat head faster (and achieve a greater velocity at any given instant; see: momentum) and/or they can increase the radius of the circle about which they are rotating (i.e. increase their swing length; see: moment of inertia). Doing either (or both!) will increase momentum and torque. (So, of course, would increasing the mass of your bat, i.e. swinging a heavier one—but only if doing so cost you little or no bat speed.)

We can see this theory in practice by looking at the relationship between average bat speed and average swing length among MLB hitters. The correlation between the two is 0.54, indicating a moderate (bordering on strong) relationship between the two variables. Basically, the longer an individual’s swing (i.e. the larger the radius of the circle), the faster their swing will generally be. However, swing length doesn’t fully explain swing speed (the correlation isn't 1.0, after all) because swing speed can be modulated by other variables, including how quickly a hitter accelerates their trunk.

Additionally, if we consider average bat speed and Statcast’s run value statistic, it can be said that faster bat speeds have a moderate correlation with offensive production (r = 0.41). Again, bat speed is not the sole determinant of offensive production (the correlation is not 1.0), but it is an important factor.

Increasing an athlete’s swing speed, either by tweaking their mechanics to increase swing length or by improving their ability to accelerate their trunk rotation via strength training, is of vital importance for individual and team success in the long term. (Yes, Luis Arraez exists. Yes, he has a slow swing speed. Yes, he is productive. Yes, he is an exception to the rule.) However, this also means the opposite is true: a decrease in swing speed would likely have a deleterious impact on offensive production in the long run.

That brings us to Byron Buxton and Royce Lewis. Both Buxton (76.2 mph to 74.3 mph) and Lewis (75.1 mph to 73.3 mph) experienced a dip in swing speed in 2024, compared to the second half of 2023. (We don’t know how this trend compares to previous seasons because we don’t have that data.) However, it’s likely that their decreases were driven by different mechanisms.

Buxton has one of the longest swings (8 feet, in three-dimensional space, from the start of his swing to the front of the hitting zone) in baseball, which is the driving force behind both his prolific power and propensity to swing and miss. (In short, a longer swing not only causes a fast barrel but also introduces more difficulty in adjusting to a given pitch. The result: more dingers, but also more strikeouts.) From 2023 to 2024, his swing length actually increased from 8.0 feet to 8.1 feet, despite a 2-mph reduction in speed. This would seem to imply that the primary mitigating factor was that he was rotating his trunk more slowly in 2024. 

Counterintuitively, it’s possible that this reduced reliance on trunk rotation was due, at least in part, to his right knee feeling better. The back leg (Buxton’s right) is important for generating force during a swing, and that force is modulated by the hips, core, and arms before being transferred to the ball on contact with the bat. When Buxton’s right knee was in pain, it’s possible that he compensated by increasing his trunk rotation acceleration to generate similar levels of force. As such, for Buxton to regain his swing speed, it’s likely that he will have to increase his trunk rotational power via strength and weighted-bat training.

Lewis, on the other hand, saw his swing length decrease from 7.9-feet to 7.7-feet. Because torque is proportional to the square of the radius of the circle about which he is rotating, a small decrease in swing length can lead to a large decrease in torque production (assuming he used bats of the same weight during both seasons).

Lewis saw his production crater during the second half of the 2024 season, as the Twins saw their playoff odds evaporate. It’s possible Lewis subconsciously reduced his swing length to allow for better barrel control, in an effort to improve his production and right the quickly sinking ship. However, doing so is antithetical to Lewis’ strengths, primarily that of quick-twitch power. Lewis is at his best when he's swinging for the fences, not trying to hit singles. For Lewis to regain his old form, it’s possible that he just simply needs to increase his swing length. 

As we gain the ability to measure not just the outputs of players' movements (like velocity, spin rate, exit velocity, and others) but the movements themselves (like swing speed, arm angle, and more), we'll have to handle lots of new data carefully, and ask good questions about it. Buxton and Lewis exemplify the way changes in swing speed can speak to two different issues, with two different possible remedies—or even more possibilities, not fully unpacked here. Some players can't move a particular way. Others choose not to, for strategic reasons. Either way, it's helpful to understand how they're moving. From there, it becomes possible to convert problems into solutions.

View full article

[Mark G]

Is anybody else's head spinning?  😳

[Whitey333]

It's crazy.  It's insane.  It's the new wave of analytic bs that is ruining the game.  Bottom like is Buxton and Lewis have not nearly lived up to their hype.  It's time for both to put up or shut up.  They both need to play full time for a full season and produce at or near their expectations or move on from both of them.

[Original_JB]

As a fan, I love this stuff (analysis) because, you know, "science"; But I don't want to put this kind of info in Rocco's hands......

So, since you have all the data (at least for BB and RL), do we see any variation depending upon whether they are facing a 'same' or 'opposite' handed pitcher?

Ooh, and how about, does the data match up with the old adage of "shortening up the swing with two strikes to make better contact/protect the plate"?

[Coach Wheels]

I'll be showing my age with this response but I don't care what your swing speed is if you consistently strike out with runners in scoring position. Put the ball in play and the rest will take of itself. 

[In My La Z boy]

16 minutes ago, Original_JB said:

As a fan, I love this stuff (analysis) because, you know, "science"; But I don't want to put this kind of info in Rocco's hands......

So, since you have all the data (at least for BB and RL), do we see any variation depending upon whether they are facing a 'same' or 'opposite' handed pitcher?

Ooh, and how about, does the data match up with the old adage of "shortening up the swing with two strikes to make better contact/protect the plate"?

Exactly this! Analytics & Data, and all these advancements in measuring results are a beautiful thing for the front office, and a curse for managers. A good friend of mine is an NCAA record holder in basketball, and had some big time skills. We talk about some of his games. When he was at his best and just filling it up in front of 20,000 people he was "in the zone", and he describes this as a state of consciousness where he is simply reacting out of instinct, no thinking, almost floating around the court. Like Gretzky used to say "I skate to where the puck's going to be" - I remember Buxton commenting a few years ago on this topic. He is also at his best when he isn't thinking but reacting instinctively. How do you put all these analytics into someone's head, and then get them to play out of instinctive reaction? You need a HIGH IQ to pull this off. Absorb the nitty gritty analytics, but clear out your mind when you step between the white lines? 

[Matthew Trueblood]

41 minutes ago, Original_JB said:

As a fan, I love this stuff (analysis) because, you know, "science"; But I don't want to put this kind of info in Rocco's hands......

So, since you have all the data (at least for BB and RL), do we see any variation depending upon whether they are facing a 'same' or 'opposite' handed pitcher?

Ooh, and how about, does the data match up with the old adage of "shortening up the swing with two strikes to make better contact/protect the plate"?

This is a great set of questions, JB. Yes, we have all of that, with a bit of digging! I (foolishly) take reviewing it a bit for granted; we should do better at bringing you that kind of detailed info. I think we'll do a piece centered on this soon. 

In the meantime:

Byron Buxton, Swing Speed: 

0 Strikes: 75.0 MPH
1 Strike: 74.5
2 Strikes: 73.4

Royce Lewis:

0 Strikes: 74.0
1 Strike: 74.0
2 Strikes: 72.1

Like most hitters, they *do* slow down their swings a bit to increase their contact rates with two strikes. This is why it's important to get ahead in counts; most guys give up some power when they fall behind.

[chpettit19]

20 minutes ago, In My La Z boy said:

Exactly this! Analytics & Data, and all these advancements in measuring results are a beautiful thing for the front office, and a curse for managers. A good friend of mine is an NCAA record holder in basketball, and had some big time skills. We talk about some of his games. When he was at his best and just filling it up in front of 20,000 people he was "in the zone", and he describes this as a state of consciousness where he is simply reacting out of instinct, no thinking, almost floating around the court. Like Gretzky used to say "I skate to where the puck's going to be" - I remember Buxton commenting a few years ago on this topic. He is also at his best when he isn't thinking but reacting instinctively. How do you put all these analytics into someone's head, and then get them to play out of instinctive reaction? You need a HIGH IQ to pull this off. Absorb the nitty gritty analytics, but clear out your mind when you step between the white lines? 

It's the manager (and coaches) job to know what each player wants and needs to perform. Not every player gets the same info. Correa loves this stuff and wants all the data he can get. How good each coach/manager is at disseminating the information is the question. But it's an individualized thing. If Buxton only wants to see X, Y, and Z but Correa wants A through Z then Buxton gets X, Y, Z and Correa gets A through Z. It's only a curse if the manager is bad at their job.

[In My La Z boy]

1 minute ago, chpettit19 said:

It's the manager (and coaches) job to know what each player wants and needs to perform. Not every player gets the same info. Correa loves this stuff and wants all the data he can get. How good each coach/manager is at disseminating the information is the question. But it's an individualized thing. If Buxton only wants to see X, Y, and Z but Correa wants A through Z then Buxton gets X, Y, Z and Correa gets A through Z. It's only a curse if the manager is bad at their job.

Exactly as JB said. I've lost confidence in Rocco to handle his players properly no question.

[Lucas Seehafer PT]

27 minutes ago, In My La Z boy said:

Exactly this! Analytics & Data, and all these advancements in measuring results are a beautiful thing for the front office, and a curse for managers. A good friend of mine is an NCAA record holder in basketball, and had some big time skills. We talk about some of his games. When he was at his best and just filling it up in front of 20,000 people he was "in the zone", and he describes this as a state of consciousness where he is simply reacting out of instinct, no thinking, almost floating around the court. Like Gretzky used to say "I skate to where the puck's going to be" - I remember Buxton commenting a few years ago on this topic. He is also at his best when he isn't thinking but reacting instinctively. How do you put all these analytics into someone's head, and then get them to play out of instinctive reaction? You need a HIGH IQ to pull this off. Absorb the nitty gritty analytics, but clear out your mind when you step between the white lines? 

This is a really good point. Essentially, a good coach could take this data and tell Buck, "Hey. When you're swinging, try and rotate your hips as fast as possible." For Lewis, "Stick your arms out a little further with each swing." They'd then work on drills that reinforce those movement patterns. Therefore, the pass on the concepts with even uttering the word torque or moment of inertia.

[chpettit19]

1 hour ago, Original_JB said:

As a fan, I love this stuff (analysis) because, you know, "science"; But I don't want to put this kind of info in Rocco's hands......

So, since you have all the data (at least for BB and RL), do we see any variation depending upon whether they are facing a 'same' or 'opposite' handed pitcher?

Ooh, and how about, does the data match up with the old adage of "shortening up the swing with two strikes to make better contact/protect the plate"?

I have some bad (well, I'd argue good) news for you...Rocco has this kind of info and so much more. The teams have everything we do and so much more you wouldn't even believe. They have their own teams designing different metrics and hire outside agencies (Sports Info Solutions, Inside Edge, etc.) to track certain things for them. They can track these kinds of things in real time. Rocco (and every smart MLB team) has been using pitcher data to make decisions for years. It's part of why the Twins have had such a healthy rotation for so many years. They track release points (arm angle and extension) as part of the decision making process for when to pull pitchers as it's a clear sign the pitcher is getting tired when their release points start changing enough.

If you're into this kind of stuff, I'd definitely suggest playing around on Baseball Savant's page for bat tracking. You can sort by pitcher handedness, batter handedness, count, pitch type, all kinds of things. It's fascinating stuff. At least I find it fascinating.

[chpettit19]

4 minutes ago, In My La Z boy said:

Exactly as JB said. I've lost confidence in Rocco to handle his players properly no question.

I'm not sure how we'd have any way at all to determine how good he is at this particular part of his job. But to each their own. 

[In My La Z boy]

9 minutes ago, chpettit19 said:

I'm not sure how we'd have any way at all to determine how good he is at this particular part of his job. But to each their own. 

I am measured on results versus last year, versus competition, and versus the bottom line. I need to get the very best out of my players as much of the time as possible. This would be how I measure Rocco.

[saviking]

2 hours ago, Mark G said:

Is anybody else's head spinning?  😳

One of those articles you scroll down in search of the conclusion, hopefully, in a nutshell

[NotAboutWinning]

I think this is where the hitting coach makes a difference. It seemed, at times, Popkins was overwhelming hitters with too much to think about. Hopefully, Borgschulte is better at tailoring it to each hitter!

[Rod Carews Birthday]

Fascinating read!  I don’t know that it helps fans much to know the specifics of this, but it certainly illuminates some of the high level analytics that teams, coaches, and players have at their fingertips.  Back in the day, managers would only have the eye test to say “well I think that’s a pretty fast swing,” which is nothing if not biased and a wild guess filled exercise. And this is just the tip of the iceberg!

[Ruven]

Great stuff. Well done. Really clear.

Here’s my request to the numbers guys. Baseball is played in feet, not miles. Miles per hour is not the optimal unit of measurement to describe bat and ball speed. Using mph for pitches and batted balls gives no context within a ballpark or the diamond or the battery except as a relative standard. It would all make more sense in feet per second.

Eventually everyone would understand (intuitively, if not as a witness) the difference between a fastball coming out of the pitcher’s hand at 140 fps vs an off-speed pitch approaching at 120 fps, and what that meant for the batter, or that a ball rocketing at the third baseman at 150 fps was scorched while a grounder trundling along at 100 fps was utterly routine.

That is, fps is better than mph for easily translating that unit of measurement to a baseball field.

And here’s to good health for all. 

[jmlease1]

53 minutes ago, Ruven said:

Great stuff. Well done. Really clear.

Here’s my request to the numbers guys. Baseball is played in feet, not miles. Miles per hour is not the optimal unit of measurement to describe bat and ball speed. Using mph for pitches and batted balls gives no context within a ballpark or the diamond or the battery except as a relative standard. It would all make more sense in feet per second.

Eventually everyone would understand (intuitively, if not as a witness) the difference between a fastball coming out of the pitcher’s hand at 140 fps vs an off-speed pitch approaching at 120 fps, and what that meant for the batter, or that a ball rocketing at the third baseman at 150 fps was scorched while a grounder trundling along at 100 fps was utterly routine.

That is, fps is better than mph for easily translating that unit of measurement to a baseball field.

And here’s to good health for all. 

That makes a ton of sense...but it's hard (especially in a game as obsessed with tradition as baseball) to break old habits and we're talking a loooooong history of pitches being measured in mph, which has led to everything else going on that standard. It's why some people objected to OPS (and probably still do) as a stat, because they couldn't grok it instinctively the way they did a .300 BA.

right now, people "know" what a 95 mph fastball "means". It'll take a lot before people can say the same about 140 fps.

[BillyBallLives]

I prefer to keep things simple, like Gary Gaetti:

"I always swing hard in case I hit it."

[Jocko87]

Very cool data but the real value will be a couple years out when the dataset is larger and more comparisons can be made.  Not knowing what Buck has done traditionally is a bit of a hole for the comparison.

I'd also be curious what the league averages are and how some hitters that got hot late in the season stacked up.

It feels like it should decrease a bit for most hitters late in the season. What were they at leaving camp vs September?

[JD-TWINS]

I get a kick out of the fact that people at TD think data is good for the player’s consumption, the position coaches consumption, the FO consumption & the fans as well. But Rocco having data (a guy who averaged 3.0 WAR & .290 BA & .775 OPS over his first 3 seasons) is a bad thing as he’s clueless regarding hitting and most things baseball related.

[terrydactyls]

In summary, extend your arms and rotate your hips.  That was how it was explained to me in the 1950's.

[LA Vikes Fan]

2 hours ago, Lucas Seehafer PT said:

This is a really good point. Essentially, a good coach could take this data and tell Buck, "Hey. When you're swinging, try and rotate your hips as fast as possible." For Lewis, "Stick your arms out a little further with each swing." They'd then work on drills that reinforce those movement patterns. Therefore, the pass on the concepts with even uttering the word torque or moment of inertia.

It may even be simpler than this. tell Buxton he could hit better with better core strength and have him exercise in a way to improve that strength.  He will then increase his swing speed if his swing doesn't change or his body will naturally compensate with a slightly shorter swing to maintain his balance, both good results. With Lewis, tell him to swing had and to worry about SOs, his swing lengthens, and his bat speed increases. I know its not this easy but this would help both guys.   

[old nurse]

The PT missed one thing that could have contributed to the slightly slower bat speeds. The ability to step, twist, drive and swing has a strength component and a flexibility component. The wear and tear of the season will affect the strength and the flexibility of the player. As they accumulate the data, this actually may be a trend for most players to slow down, or most of the injury prone players to slow down ever so slightly. 

[Parfigliano]

1 hour ago, jmlease1 said:

That makes a ton of sense...but it's hard (especially in a game as obsessed with tradition as baseball) to break old habits and we're talking a loooooong history of pitches being measured in mph, which has led to everything else going on that standard. It's why some people objected to OPS (and probably still do) as a stat, because they couldn't grok it instinctively the way they did a .300 BA.

right now, people "know" what a 95 mph fastball "means". It'll take a lot before people can say the same about 140 fps.

140 fps = 95.45 mph

[Linus]

Interesting- thanks.  There is another aspect to this.  While swinging a heavier bat supplies more for the mass part of the equation for some guys swinging a lighter bat at greater velocity results in the most force.  Each player has to find their optimal combination.

One of the Twins greats, Harmon or Tony switched to a lighter bat towards the end of the season for this reason.

[shimrod]

 

"How do you put all these analytics into someone's head, and then get them to play out of instinctive reaction? "

You do that by using the analytics to influence and inform PRACTICE. Never the game.

If, during a game, you're standing at the plate thinking of your mechanics you're already toast. 

 

[Matthew Trueblood]

1 hour ago, Linus said:

Interesting- thanks.  There is another aspect to this.  While swinging a heavier bat supplies more for the mass part of the equation for some guys swinging a lighter bat at greater velocity results in the most force.  Each player has to find their optimal combination.

One of the Twins greats, Harmon or Tony switched to a lighter bat towards the end of the season for this reason.

I think that was somewhat common back then, but specifically, Tony O did it, after learning to do so from Rod Carew. Carew was fanatical about bat weights and unafraid to change things up when he sensed a need for that.

[bean5302]

The Baseball Bat Bros on youtube tested out some historic bats. Honus Wagner, Joe Jackson, Babe Ruth, Mickey Mantle, Jackie Robinson, etc.
 

Fun video to watch for sure.

I don't think much can be pulled in terms of swing speed from Royce Lewis. The guy couldn't even run by the end of the year with major lower body injuries that sapped all his athleticism. 

[Jocko87]

Lots of comments about how the coaches can work with this but they’ve had this data and more for a long time.  It’s just now being published so we can see it.  

The golf example is a good one for several reasons.  We are just now seeing affordable consumer golf simulators that can measure what the pros have been working with for years.  The instant feedback is fantastic for grooving and practicing feels.  In both sports they are trying to maximize efficiency while still keeping the wear and tear of a redundant motion to a minimum.  

One of the main reasons golfers speed train for a faster swing is not because they will swing that hard all the time but because it raises the average cruising speed allowing more control at higher speeds.  Same with baseball, a full effort swing would seem to tie in with more swing and miss. 

Here is a good example of what they are doing in golf.  It wouldn’t take too much imagination for something like a driveline for hitters doing something similar.  It’s probably happening already but the pitchers get most of the attention.