Did Fernando Tatis Jr's Mechanics Fall Out Of Whack In Leading To This Spiral?

A couple of weeks ago, I speculated that pitchers were adjusting to Fernando Tatis Jr. by incorporating more off-speed pitches. There wasn't a drastic change in his overall zone approach, but that pitch type was clearly something he was struggling with. That, in itself, was one possible explanation for the struggles we're about to explore from a different angle.

Since the midway point of May, the San Diego Padres have been one of the worst offensive teams in baseball. They rank 27th in the league in runs scored (83), 29th in the league in on-base percentage (.284), and dead last in their power output (.115 isolated power). Even an 11-run outburst against the Los Angeles Dodgers earlier this week and an absolutely torrid stretch from Manny Machado haven't mattered, considering the bottoming out of essentially the entire lineup. 

Central to those woes since May 15th is Fernando Tatis Jr. Despite sitting on pace to eclipse last year's Wins Above Replacement figure — he's at 2.7 after a 3.2 mark in 2024 — it's the output from March & April that's doing a lot of the heavy lifting as far as his overall numbers go. 

That iteration of Tatis atop the lineup was a marvel. He very much looked like he regained superstar status, given a .345/.409/.602 line that accompanied a .257 ISO and a 184 wRC+. That was not only leading the Padres' strong lineup to start the year, but also planted him firmly in the middle of early National League Most Valuable Player discussion. The discussion since has been... not that. 

The point in time to which we can point where Tatis' struggles began was following a hit-by-pitch in Pittsburgh back at the beginning of May. He returned to the lineup on May 3rd without requiring any kind of IL stint. However, the numbers since that point are, objectively, quite bad. 

In the time since that HBP on his forearm, Tatis Jr has been the team's worst hitter by wRC+ (76). He's hitting just .188, reaching base at a mere .277 clip, and ISOing at a rate of just .145. The first two numbers are also the team's worst in that stretch, with his isolated power checking in behind only Machado (.232) and Gavin Sheets (.221). His strikeout rate remains manageable (21.3 percent) and his walk rate is completely acceptable, as a 10.3 percent rate trails only Jake Cronenworth (14.3) & Xander Bogaerts (10.7) for the team lead.

Whether the HBP is central to the story here is impossible for us to ascertain. We're not in the clubhouse or the training room. But it does represent a fixed point in time between the two versions of Tatis Jr that we've seen thus far in 2025. The off-speed component we've explored does offer one potential explanation. But with new bat tracking data available from Statcast, is there something we missed? 

The following is the breakdown of Tatis' swing metrics through May 2nd: 

And here is where he's sitting in each regard since May 3rd: 

The bat speed has increased slightly. It's also gotten slightly longer, with a 7.1-foot average in March & April and a 7.3 average since the start of May. Faster and longer, on its own, isn't entirely ideal when you're struggling to make contact, especially against one type of pitch. It gained about two miles per hour against off-speed pitches in May and became slightly longer. This certainly supports the element of struggle against off-speed pitches. 

What else is here that we might've missed at first blush? The swing path tilt has dropped. Similarly, the attack direction has also changed. But neither has deviated from his initial production to indicate any massive mechanical change. You might note, however, that there has been a substantial change in his footwork. While we can't isolate a visual difference between the two points in time, it's a rather notable change that's more of a reversion to his setup from last season. 

Tatis has spread his feet a bit more and gotten much more closed since our May 3rd framing. It's still a much more open stance than his 29-degree stance from 2024, but it does represent a fairly notable mechanical change. Is it a change that is, perhaps, messing with his timing on some level? It's possible. In addition to a contact rate that's roughly three percent lower between the two timeframes, he has also seen a three-mile-per-hour drop in average exit velocity (94.1 MPH to 91 MPH) and, notably, a more than 17 percent drop in Hard-Hit% (54.7 to 37.0 percent). 

It's difficult to pinpoint the exact issue here and the reason behind it. But it wouldn't be entirely unreasonable to say that after that hit-by-pitch, Tatis Jr changed something in the way he swings the bat. We can't speculate on whether it was to compensate for any level of pain, but a clear change in the way he's swinging has manifested in the games since May 3rd. This is on top of the off-speed struggles he was already facing, due to the opposing pitcher's adjustments. 

So, where exactly do you go from here if you're Fernando Tatis Jr. It's a question he needs to answer in a rather expedient fashion, given his importance to this Padres' offense in figuring it out as we move into the second half of the month.