Anatomy of a Slump

The Recent Struggles of Fernando Tatis Jr: Luck or Process?

The Dodgers series is thankfully behind us and we can debrief a bit. The series was, in large measure, a disappointment and seemed to be a representation of everything that has plagued this team so far in 2023: lack of hitting with RISP, bullpen woes, starting pitching depth woes, Josh Hader usage woes, umpiring woes, unlucky home run woes (on both sides of the ball), and slumping stars woes. It wasn’t all bad though. Ha-Seong Kim continued to show why he’s deserving of a contract extension and recognition from the baseball world as a premier leadoff hitter with an elite glove. Jake Cronenworth also continued his offensive resurgence, showcasing (or returning to) a compact swing designed to hit the ball hard to all fields. Gary Sanchez continues to be one of the best waiver-wire pickup this season (maybe all-time?). Luis Campusano had another banner day at the plate on Monday afternoon going 4-4 with two home runs, which was unfortunately overshadowed by the Seth Lugo’s fourth inning meltdown. Finally, Fernando Tatis Jr. broke out of a three-game hitless streak with a 2-RBI double on Monday afternoon. But there are concerns that he’s mired in a larger slump. This last point bears some discussion.

If it seems like Fernando Tatis Jr. has been bogged down in one of the worst slumps of his career since the all-star break, it’s because he has been:

He has seen his OPS drop to under .800 (his career OPS is .919). Looking only at outcomes from his at bats since the All-Star Break, it’s hard to argue against this point. But the eye-test, and more importantly, the data says there’s more to the story. Here’s his first at bat Friday:

Source: Baseball Savant

This looks a lot like the home-run-that-wasn’t against Pittsburgh. We speculated then that perhaps spin was to blame for the ball seeming to ‘die’ at the wall without strong wind as a factor. Tanner Stokey of Driveline Baseball believes this is the exact explanation:

The Twitter thread (both of those terms might be wrong now) is worth reading but doesn’t offer much supporting evidence for the assertion. Driveline Baseball advertises itself as “the premier data-driven baseball player development organization in the world” and perhaps not sharing the data directly is like not sharing the secret recipe for Coca-Cola. In any case, this really seems to raise more questions, like, why now? Has Tatis always had this ‘problem’? It seems a little dubious without supporting evidence. Stokey notes that hitting with ‘true spin’ is a teachable skill. It’s entirely possible that’s the case but before suggesting Tatis rework his swing it would be important to actually see some supporting data.

Regardless of whether spin played a role in Tatis having two home-run balls turn into outs in the past two weeks, he’s been hitting the ball fairly well overall and certainly having some degree of bad luck as @TooMuchMortons_ noted:

This appears to be part of the explanation: Tatis is definitely in an ‘Outcomes’ slump, but his process has been pretty good. He’s been hitting the ball hard, but not getting hits. But there is a little bit more to the story here as well. Look at the data from Baseball Savant and a pretty clear picture begins to develop:

In 2023 he’s putting the ball in play a lot more, 20.7% (310 of 1510) of the pitches he sees compared to his career average before 2023 of 15.9%. He’s at a career low 3.52 pitches seen per plate appearance. You can see all of this reflected in his lower strikeout and walk percentages. But what you see in the Hard Hit percentage is that although he’s putting it in play much more often, the extra balls in play aren’t being hit hard. In 2021 he put 329 balls in play, 183 were hard hit, 55.6%. In 2023 he’s put almost the same number of balls in play 310, but only 154 were hit hard, 49.7%. This is explained by his chase rate deteriorating:

There’s something here. Tatis has become more of a free swinger:

He’s chasing 33.4% of pitches out of the strike zone (21st percentile), and he makes contact with a lot of them. Also, look at that 1st Pitch Swing percentage. The league has likely taken notice as the year has gone by that Tatis is swinging at more than 50% of first pitch offerings. In the Dodgers series Tatis swung at the first pitch ten times across four games. The Dodgers did not give him a single first pitch over the heart of the plate.

Here are his percentiles for barrel percentage and exit velocity:

Tatis is down to the 73rd percentile in barrel percentage, that would be a good percentile for most players, but it is far far below where Tatis has been in years past. Again, he’s putting the ball in play a lot more but it seems that many of the extra balls put into play are non-barrel, softer contact which is diluting his average exit velocity and barrel percentage. It’s not a coincidence that both the barrel percentage and exit velocity have trended inversely to his chase rate. This is the reason. As the season has gone on it’s likely the league has taken notice of the trend and is pitching Tatis more to poor contact.

None of this is to say he’s having a bad season. Tatis’ Statcast projections show an expected batting average of .299, top 3% in the league. His expected weighted on base average is still top 5%. This is fantastic for most players. But it’s down from his career averages, and there does seem to be a potentially exploitable weakness developing. MLB teams are smart and will have undoubtedly taken notice of Tatis’ tendencies and are game planning for it.

To summarize, Tatis seems to be in a short term slump that is largely the result of hitting the ball well and getting some unlucky outcomes. But the longer term trend on the season is that he’s swinging more freely, and as a result putting a lot more balls in play softly than in years past. Because he’s Fernando Tatis Jr his ‘down year’ is still better than most MLBers, but it’s probable that a little more selectivity on the pitches he hits will translate into results more typical for the Nando we’re all familiar with.

Tatis is so good that it wouldn’t be shocking if he went on a tear, and his end of year Statcast metrics were in line with his career norms. We can hope. But we should also be prepared to see further performance degradation if the free swinging is a more durable challenge for him to solve.

On to Seattle for the latest installment of “the most important series of the year.”

Go Padres!