UTK Special 6/16/26
Hamageddon III: Revenge of the Hamates
AJ Pierzynski said something very interesting on Foul Territory on Monday:
Pierzynski’s Trajekt theory makes enough sense that it shouldn’t be dismissed, which is not the same as saying it’s proven. That distinction matters because baseball loves finding the villain after an injury cluster. Sometimes the villain is the wall, sometimes the pitch clock, sometimes the weight room, sometimes a machine that costs more than most houses and throws Paul Skenes at you under the bleachers. Convenient villains are useful. They’re not always correct.
The hamate is a tiny wrist bone with a hook-shaped projection sitting near the base of the pinkie-side of the hand. For hitters, the hook is in a terrible neighborhood. It sits right where the bat knob, bottom hand, grip pressure, and rotational force all meet. The injury is common enough in baseball that “remove the hook, wait six weeks, rebuild grip strength” has become almost casual language, which undersells how disruptive it can be. The pain source comes out quickly. The power sometimes takes longer to come back. The hand heals before the hitter does.
The argument for Trajekt involvement is pretty straightforward. Trajekt Arc lets hitters take real swings against real baseballs modeled on actual pitchers, using data and video to replicate release point, velocity, spin, and pitch shape. It has gone from novelty to near-ubiquity quickly, with the Washington Post reporting Trajekt had been confirmed with 25 MLB teams and more than 70 machines across pro leagues globally. Unlike VR, hitters aren’t just recognizing pitches. They’re swinging at them, often with intent.
That matters because hamate fractures are often cumulative. The Wall Street Journal did a good job earlier this spring connecting the recent rash of hamate injuries to modern bat speed obsession and bottom-hand grip style, where hitters wrap around the knob, sometimes with the pinkie off, creating repeated focal pressure into the hook of the hamate. Bobby Tewksbary described the grip as feeling “whippier,” while Dr. Thomas DiLiberti compared the knob’s effect to a ball-peen hammer repeatedly striking a fragile bone. Corbin Carroll, one of the spring’s hamate cases, summed up the future bleakly enough: “Not the first person this is going to happen to. Not the last.”
Now add Trajekt. More high-intent swings. More high-velocity reps. More game-like timing. More chances for mishits, jams, emergency swings, and bottom-hand stress. The machine’s entire selling point is realism. Buster Posey told the San Francisco Chronicle that a machine replicating velocity, spin, and shape gives hitters the closest look at a pitcher’s actual pitch, while Willy Adames and Matt Chapman were more cautious, with Chapman saying the machine was hard to time and “funky,” and Adames saying he didn’t want to feel like he was battling elite arms in the cage before the game.
That’s the pro-Pierzynski side. If hitters are taking hundreds of additional game-intent swings against nasty, high-velocity, high-movement pitches, and if the modern grip already concentrates force onto the hamate, then Trajekt could be an accelerant. Not the match, maybe, but the oxygen.
The other side is just as important. Hamate injuries existed long before Trajekt. Baseball players, golfers, and hockey players have fractured the hook of the hamate for decades because gripping an implement and applying force through the palm is exactly how you irritate that structure. The hamate is also commonly missed on initial X-rays and prone to complications because of its blood supply, which means we may also be diagnosing and reporting these better than before.
There’s also the question of actual exposure. We don’t know how many swings players are taking off Trajekt, who is taking them, at what intensity, with what bat, using what grip, or whether those players are disproportionately represented among hamate cases. Teams do track this internally, but publicly we don’t have anything close to an injury-rate denominator. “A lot of hamates happened in a year when Trajekt became common” is interesting. It is not evidence by itself. Many of these teams had Trajekt in years past, with no evidence it was concentrated in teams that did.
Let’s go one more: we know that Driveline has a Trajekt. There’s no evidence that their players are having more hamate injuries and we know those players are getting more swings in the offseason. I reached out to Driveline for comment and did not get an official response in time for publication.
There’s another confounder: Trajekt may simply be one piece of a larger hitting culture that already created the risk. Everyone is chasing bat speed. Everyone is optimizing swing decisions. Everyone wants more game-like reps, leading to more live BP sessions and sim games, even in the offseason. Trajekt might be visible because it’s new and expensive, while the real cause is broader: harder swings, knob-loaded grips, more year-round hitting, more machine work, and a sport that has decided power is worth almost any toll until the hook snaps.
My soft conclusion is this: Pierzynski is probably pointing at something real, but maybe not the whole thing. Trajekt seems more likely to be a contributor than a root cause. The mechanism makes sense. The timing is suspicious enough to study. The player comments about intensity and realism support the idea that these are not ordinary flips in the cage. But there’s very little public evidence tying Trajekt directly to hamate injuries, and without team-level swing volume and injury data, anyone claiming certainty is selling harder than the machine.
Baseball should study it. Quietly, seriously, without turning it into another technology panic. Count swings. Track grip. Track mishits. Track hamate soreness before fractures. It should be as simple that the hitters taking the most swings should be at the most risk and that data is knowable. If Trajekt is helping hitters win at the plate while quietly loading one of the smallest bones in the wrist like a tiny anvil, teams need to know that before the next wave of “routine” surgeries becomes routine for the wrong reason.