Fernando Tatis Jr. Is Unlocking His Defensive Potential

Written by: Justin Choi (@justinochoi)

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30-something games into an abbreviated season is all it took for us to realize an obvious truth: Fernando Tatis Jr. is the most exciting player in baseball. Hitting .317/.379/.590 (150 wRC+) in his rookie season wasn’t enough – this phenom has managed to refine just about every tool he has. Hitting for power? Tatis leads the league in Hard Hit rate. Plate discipline? He’s increased his walk rate and decreased his strikeout rate, which a lower O-Swing% backs up. Baserunning? He’s swiped 7 bags so far without getting caught once. 

But there’s been one improvement to Tatis’s game that many have overlooked. While he resembles an ideal five-tool player, defense has never been a strong point. This year however? Tatis Jr. looks like a legitimate shortstop. 

Saying that his defense was once mediocre seems puzzling – a quick search on Youtube gives you multiple defensive highlights to enjoy. What if I were to use advanced defensive metrics as evidence? DRS rated him as two runs below 731.1 innings fielded last year, and that’s the most optimistic view. UZR and Statcast’s infield OAA, which were more pessimistic, pegged him as 5.8 runs and 13 outs below average, respectively. 

Sure, defensive metrics are the least reliable of the sabermetrics crop, and they take forever to stabilize. Perhaps 84 games weren’t enough to gauge the defensive capabilities of Fernando Tatis Jr. But this is one of the few instances where we can turn to the eye test and say, yes, Tatis was not a good defender last year. Why? Here’s an example: 

This is a throwing error: 

And here’s one that’s much, much worse: 

Notice a trend? A large chunk of Tatis’s errors are on routine plays – plays that involve more reflex than actual thought for many shortstops. Errors in baseball are flawed due to their subjective nature, but in the above three GIFs, it’s safe to say that Tatis is solely responsible for the on-field miscues. 

Advanced metrics agree. Breaking down Tatis’s appalling -13 OAA last year, the third-worst amongst all qualified shortstops, 8 of those 13 are from attempts that had an estimated success rate between 75% and 100%! The examples I’ve shown clearly aren’t cherry-picked. 

Still, his defensive plays were plastered on social media, and they are impressive no matter how you look at them. That’s because when his speed and athleticism did come together, we saw a glimpse of his ceiling: 

To wit, if we change the success rate from 75% ~ 100% to 0% ~ 25%, Tatis had two outs above average. That’s right – he generated more value by handling the most impossible balls than he did by tossing routine grounders to first. Even though a defender receives more credit for an ‘out above average’ on difficult plays, it’s amazing nonetheless. In short, his highs were high, and his lows were low. 

This something many analysts, including Ben Clemens of FanGraphs, noticed after Tatis’s rookie season. The young prospect showed promise, but would he improve next year? 

In 2020, Tatis passes both the numbers test and the eye test. By DRS, he’s one run above average in just 305.1 innings fielded, and his UZR/150, which is simply regular UZR divided by the average number of attempts in a season, is 3.2. However, it’s once again important to mention that defensive metrics take years to stabilize. As evidence, look no further than the fact that Andrelton Simmons is ranked 29th on Fangraphs’ defensive runs leaderboard. 

But for someone whose defensive run totals were consistently in the red, this change is encouraging despite a minuscule sample size. Moving to the eye test, consider this GIF of Tatis fielding a routine grounder in 2020: 

It clocks in at 6 seconds, but from it there’s a lot we can observe. First, Tatis isn’t recklessly dashing towards the ball; rather, he lets the ball roll towards him, and from a secure position scoops it up. From there, instead of airmailing it, he takes a few sidesteps in preparation for the throw, perhaps knowing that his powerful arm will make up for lost time. 

Tatis’s handling of the ball represents more confidence in his skill, even a hint of maturity in that he isn’t anxious to get an out right then and there. This doesn’t mean Tatis is any less aggressive, however. He still acts quick when necessary, and what’s impressive is the added accuracy and precision at which he does so. Check out this gem against the Rangers: 

The first part – when he backs up behind the ball and catches it – is the new Tatis. The second part, the laser-beam throw to nab Dietrich, is the flash of brilliance seen last year that didn’t always translate into success. A 95-mph throw is impressive, but even more so when it results in an out: 

That throw, which happened on Wednesday this week, was the fastest throw of Tatis’s career according to Statcast. So he’s improved his accuracy and his raw arm strength? That is terrifying to consider. 

It’s also impressive how Tatis is willing to improve despite his ascension to superstardom. The best players, after all, are the ones who continue to strive for greatness long after their MLB debuts. Such mentality is equally as remarkable as the mammoth home runs he hits and the incredible pace at which he legs out a triple. Tatis Jr. is truly special. 

Of course, Tatis being Tatis, there will be many moments in a career when he’ll attempt ridiculous and reckless plays, those that exist outside the realm of catch probability and sprint speed. Such a play occurred on August 23rd. And as it unfolded in mere seconds, no numbers crossed my mind. Here’s Air Tatis: 

Follow P365 MLB and KBO Analyst Justin Choi on Twitter! @justinochoi

Follow us on Twitter! @Prospects365

All statistics from Baseball Savant and Fangraphs

Featured image courtesy of photographer Charles LeClaire and USA Today Sports

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