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# Exploring Vladimir Guerrero Jr.’s Batted Balls: Comparators

Part 2: Comparators

Yesterday, I looked into how Vladimir Guerrero jr. hits the ball. The short version is that he hits it very hard, but way too often on the ground. Because we still have a relatively small sample of work on which to judge Guerrero’s results, especially given that he gained significant power from 2019 to 2020, I want to identify players who strike the ball similarly to see what that might tell us about how his approach could play out in the longer term.

I didn’t want to just use average launch angle and exit velocity to do that, because the shape of those distributions is really important. A hitter who hit all of his balls in play at exactly 88mph and one who alternated between hitting them 70mph and 105mph would both be around league average for exit velocity, but the former would probably hit almost no home runs while the latter would hit tons. One who hit all his batted balls at a 20-degree launch angle would run a great BABIP, one who alternated between -5 and 45 degrees would have the same average but almost never get a hit. Things get even more complicated when you factor in correlation between the two (batters hit the ball harder at launch angles near zero, for example, but not everyone’s swing produces the best contact at the same angles). As we saw yesterday, Guerrero’s hardest contact comes at low launch angles, and his huge power hasn’t totally translated to balls hit in the air. Flattening all that into one number risks missing important details.

Because of that, I wanted to look at the shape of batters’ whole distributions of batted balls. To do that, I relied on a statistical approach called the crossmatch test. Essentially, what the test does is take a list of samples from two distributions (like a list of exit velocities and launch angles from two hitters) and, using an algorithm, sorts the list into a set of the closest possible pairs. By looking at how often samples from one distribution pair with samples from the other distribution, we can calculate how likely it is that the underlying processes behind the two distributions are the same. If samples from distribution A pair with ones from distribution B pretty often, the two distributions might be generated from the same process. If samples from A are paired mostly with other samples from A and samples from B are paired mostly with samples from B, then A and B probably come from very different processes. In this case the ‘process’ is a hitter’s swing, which generates a set of observed launch angles and exit velocities, and by looking at that set of observations we’re trying to figure out whose swing hits the ball about the same way Vlad’s does.

I took all balls hit into play (defined as all fair balls including home runs and any balls fielded in foul territory) from 2017 through 2020 and grouped it by season to account for changes like the juiced ball in 2017 and 2019. I assigned each ball in play a percentile rank for exit velocity and launch angle. Then I grouped the data by hitter and year, and compared each hitter-season to Guerrero’s hit balls in 2019 and 2020. I filtered down to hitters who put at least 100 balls in play, which typically takes about 145 PA in the modern era.

Table 1 shows the hitters with batted ball distributions where the number of crossmatches with Vlad’s batted balls was within a quarter of a standard deviation of what would be expected if their underlying skills were the same. I’ve included strikeout and walk rates and wRC+ for comparison, but these scores are based solely on how hard and at what angle the ball was hit.

The main thing to note here is that there aren’t very many of them. There were 1,362 player-seasons with at least 100 balls in play from 2017 through 2020, and only 4 are reasonably close matches for Vlad. By contrast, Bo Bichette in 2020 had 47 matches that would qualify for the table, Danny Jansen had 43, Lourdes Gurriel jr. had 83, and Teoscar Hernandez had 86, and each of them had at least 10 matches closer than Laureano was to Guerrero. Vlad’s combination of big power and low launch angle is very rare.

These aren’t a very encouraging set of comps, although Guerrero was better than the average because he has a much lower K rate and a higher walk rate than three of the four. All of these guys except Martin had better than average max exit velocities, though none near the top of the leaderboard like Vlad. To me, the group looks like would-be sluggers who swing at pitches they shouldn’t, which results in high strikeout and low walk rates and also in more poor contact than would be ideal. Desmond is probably the best example. His rate of Barrels (the best kind of contact, hit hard at ideal angles for extra bases) was 10.4%, way better than the 6.4% league average. On the other hand, he somehow managed to both hit ground balls at a rate almost 5% higher than average while popping up on the infield more often than average.

All of these guys except Martin have had seasons where they were very good hitters, so an approach similar to this can definitely work. They’ve also all had years were they were average or bad at the plate, though, and the differences between the two look pretty minor. The overall pattern is talent that hasn’t been consistently translated into results, probably at least in part because of swings that haven’t consistently been able to produce the right kind of contact to make use of the underlying power. That’s a concern for Vlad, although again his superior contact and plate discipline should allow him to outperform these players even if he doesn’t change his batted ball distribution. It’s also important to remember that his was his rookie season, and these hitters are all at least in their mid 20s. Not being able to reliably harness his talents at 20 is understandable, still not having done it a couple years from now would be a problem.

Table 2 shows matches to Guerrero’s 2020, using the same standards. The matches are even rarer, and outside these three the other players were also less close. Guerrero raised his average exit velocity by making less soft contact in 2020, and the result is that he’s even more singular.

It’s encouraging that these are better hitters than the previous group. Desmond was bad, and has been for years, but Pollock was excellent in 2020 and he’s mostly been a very good hitter through his career. The most interesting match, to me, is Christian Yelich. A former elite prospect who always crushed the ball but never produced the hoped-for power numbers early in his career because he drove everything into the ground? Reminds me of someone. Interestingly, Yelich’s breakout 2018 season actually came without huge changes in his average launch angle (5.0 degrees, up from 4.7 the year before) or ground ball rate (51.8%, down from 55.4%). He just managed to hit everything a little harder and to turn a handful of groundouts into line drives and popups into dangerous flies, and suddenly everything clicked. His launch angle did jump in 2019, to 11 degrees, before falling back this year (the one matched to Vlad).

Yelich is an encouraging comp, because he shows that breaking out as an elite, MVP level hitter wouldn’t necessarily require Guerrero to totally overhaul his swing. Leaning into launch angle has worked for some other hitters (which I’ll look at in part three of this series), but Yelich shows that just tightening things up with his current swing, turning a little bad contact into good, might also result in a huge improvement in his results. That’s an important point, I think, because the line between good contact and bad contact is a fine one. The figure below (the same one from Tuesday’s piece) shows that the league’s results on balls that are a few degrees or miles an hour apart can be dramatically different. A swing overhaul might work, but so might doing what he already does just a little bit better.

That said, things can also go the other way, and there are also similar hitters who fare pretty poorly. That Ian Desmond shows up in both comp groups is a bit concerning. If Vlad had just good instead of excellent power, or if his contact and plate discipline skills weren’t quite as strong as they are, he could become a pretty poor hitter pretty quickly. With his limited other skills, that would just about doom him as an everyday quality player. He’ll need to expand on his gains from 2019 to 2020, and possibly also to re-engineer his approach to generate more loft, to unlock his potential. Yelich’s down 2020 also suggests that slippage in any skills might take away any gains pretty quickly. This is a profile without a lot of room for slippage.

There are two ultimate take-aways, I think. The first is that Vlad is pretty unique, and so we should be careful in choosing any comparisons we want to apply and in interpreting anything about those comparisons. There’s no one who makes as much contact, as hard, at as low of an angle. There’s really no one close on any two of those axes, let alone all three. The second is that his ceiling with his current approach is very good, but still probably limited, and the Yelich comp suggests that a breakout might be hard to maintain. Across the last two seasons his seven close comps include one very good season, three solid ones, a poor one (twice), and an awful one. Guerrero has better plate discipline and contact skills than these comps, so he could do a little better overall than they did, but even accounting for that none of them are all-star type seasons for a first baseman. To become great, he’ll have to change his approach to hit more balls hard in the air. Next week, I’ll look at some hitters who did make a change like that, and see how it want for them.