The Brewers Are Going Through a September Bat Speed Crisis

[Matthew Trueblood]

Image courtesy of © Michael McLoone-Imagn Images

In the month of September, the Milwaukee Brewers have the lowest collective bat speed in baseball, at 70.9 miles per hour. That's not automatically a huge deal, though. This is the Brewers we're talking about, after all. Power isn't at the heart of their offensive attack, and the power they do access doesn't all come from swinging fast. They like good swing decisions, and they like good bat control, and sometimes, that means sacrificing swing speed—either by sitting guys who swing fast in favor of some who swing slower, but who deliver speed, defense and plate discipline, or by asking the regulars to cut down their swings in certain situations to suit the requirements of the moment.

Here's the thing, though: this is new. That aggregate bat speed is the lowest for the Brewers in any month of this season, and not by a small margin. In July, their average bat speed was 72.2 miles per hour; they're down by a significant margin since then. Though you don't think of bat speed first when you think about the Crew, they were middle-of-the-pack or better in that regard in each of the first four months of the campaign. Then, they were 26th in baseball in August, and now, they're dead last. What's going on here?

Any time you're looking at team-level statistics, and especially any time you're studying changes in team performance over time, check to see whether the trend is a product of changing personnel or changing performance by the same personnel. For instance, if we were looking at the Nationals, we might note that their swing speed by month this year goes:

• April: 71.6 mph
• May: 71.8
• June: 71.9
• July: 72.0
• August: 72.7
• September: 73.2

That's not necessarily because their individual hitters are doing things differently, though. They traded the slow-swinging Alex Call to the Dodgers at the deadline. They got back toolsy outfielder Dylan Crews from injury last month. They've shifted playing time toward catcher Riley Adams and first baseman Andrés Chaparro, each of whom swing faster than the players they're replacing. This is the more common way for a team's apparent profile to change within a season, in any number of ways. Jack Stern wrote about a version of this earlier this year, when the arrival of Jacob Misiorowski and some of the early shuffling in the bullpen took the Brewers from being a pitch-to-contact team to one with much better raw stuff. They didn't suddenly teach Jose Quintana to throw 98; they just brought up other players who did so. 

In this case, though, that's not what's happening. Here are eight key Milwaukee batters' average swing speed by month, from July through September:

Player	July	August	September
Jake Bauers	78.3	78.3	76.3
Jackson Chourio	74.5	75	72.8
William Contreras	74.2	73.6	72.6
Caleb Durbin	68	68.3	67.2
Sal Frelick	69.3	68.7	66.7
Danny Jansen	69.7	70.2	67.3
Joey Ortiz	73.1	71.5	70.2
Andrew Vaughn	71.5	71.4	69.8

The team certainly has needed to redistribute some playing time in recent weeks, dealing with prolonged absences from Jackson Chourio, Joey Ortiz and Rhys Hoskins. Famously, though, each of them has returned this month, so that wouldn't be much of an explanation for this phenomenon, except insofar as their replacements swung faster than they did. That's not true of, to pick a couple examples, Blake Perkins or Andruw Monasterio, so we can safely junk that hypothesis.

Besides, look at that table. Each of these guys has lost substantial bat speed since July. The group is intentionally chosen, but there are no notable counterexamples. Brice Turang, Christian Yelich, Isaac Collins, Monasterio and Perkins all have essentially held steady, but none of them have seen a surge in swing speed. There's just this octet of players with big reductions, whom we need to puzzle out.

It's tempting to guess that this is a normal trend within a season. This is pretty new data, and maybe you'd assume that everyone tires out as the year winds down. There's a scintilla of evidence of this, too, in that globally, the league's bat speed and fast swing rate (the percentage of swings that exceed 75 miles per hour) each peak in July. They're pretty darn flat from month to month, though. Remember, too, that the Brewers have dropped from the middle of the pack to the very bottom of the league. Whatever bat speed the whole league is losing, Milwaukee is losing more. In fact, they're the only team that has seen their bat speed fall by any significant or patterned amount in the second half of this year. Twenty-six teams are basically flat, and the Nationals, Astros, and Rays have each gotten a bit faster. So this isn't a normal seasonal effect at work.

Nor is it unimportant. Even understanding that swinging fast isn't at the core of Milwaukee's hitting weltanschauung, it's good to swing fast, and less good to swing less fast. Some Brewers hitters, given their other offensive traits, already flirt with having insufficient swing speed to produce much at the plate. They can get by when they're at their best (or near it), but they get into trouble in a hurry if their bats slow down markedly, the way some of these guys' have.

We can certainly go down the list and surmise a plausible reason for each player's sag. Jake Bauers, Chourio and Ortiz spent time on the injured list, and their return to play is baked into these numbers. It's possible all are still getting their timing back, and until one is back into a comfort zone and getting off one's 'A' swing consistently, that can show up as sluggish bat speed. William Contreras and Danny Jansen are catchers; enough said. I checked, and catchers do not have a different seasonal bat speed arc than the population of hitters as a whole, which is slightly surprising. Still, it's easy to imagine their bats slowing down purely because of the toll the grind takes on them and their position. 

That leaves Caleb Durbin, Sal Frelick and Andrew Vaughn, though. Durbin is as small as big-leaguers get, and has never played this much in a professional season before—even if you count his time in the Arizona Fall League last year, along with his minor-league season. He might be getting tired. Frelick has dealt with multiple minor injury issues this year; his body might be feeling the accumulation of them. Vaughn, though, is hard to explain. 

More importantly, it's hard to look at all eight of these players and accept that they're all losing bat speed purely for physical reasons, however valid each might seem in isolation. Thus, I want to advance a different theory. What if the team is using this month as a kind of hitting lab? It's possible that, at least in some at-bats, the coaching staff is asking these guys to make a more concerted effort to go the other way, or to eschew sheer bat speed for the ability to lift the ball. With enough of a cushion in terms of playoff position to lose a game here or there without losing anything of value, it's not an outrageous notion. In fact, it might be the best way for the team to approach this free month of runway before October. 

There's no way to know for sure that that's what is going on. Even if it were, the team probably wouldn't tell us; it's the kind of approach thing you want to keep clandestine. It's also possible that the players are all healthy (or healthy enough), but that their loss of bat speed isn't about instruction. Rather, it could be about a lack of adrenaline, in games that matter less than the ones they were playing a month ago. They have a terrific position practically sewn up. Adrenaline definitely plays a role in boosting bat speed for most hitters; maybe this group will just get souped up again when they can feel the danger and electricity of the postseason.

Whatever the reason for it, this is a noteworthy development. No other team is going through it this month, the way the Brewers are. Yet, they're still having competitive at-bats and playing good baseball. For now, count this first as a curiosity, and only secondarily as anything with analytical weight. In fact, for the rest of the regular season, the analytical weight of most things around the Brewers is limited. They're just gearing up, now. They've earned the right to swing a bit slower, but only for a little while.

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[steelydan]

Matthew, thanks for still another super interesting and well-written article. A few thoughts:

- I love the concept that guys are working on new approaches. No idea if it's true, but I like the idea.

- The adrenaline idea is also interesting. One thing that's unique about the Crew is their position at top of MLB win total for a long time. As Matthew stated, that can have an impact at this time of year.

- Another factor that can slow movement in an athlete is stress. The feet in particular, but it can affect anything. This idea is actually the opposite of the previous one, but as the Brewers have been playing less well and the playoffs approach, some players could be experiencing stress.

- Lastly, there could be a combination of factors at play, and those factors could differ from player to player.

[Brian]

Maybe it's because there barreled ball % is down also. They are dead last in that category I believe. Not a good trend. https://baseballsavant.mlb.com/league?season=2025#:~:text=AL East,Rockies [-43.5]