The Obvious Vladimir Guerrero Jr. Tweak

This is Carmen’s first piece as a FanGraphs contributor. Carmen is an engineer living in the Bay Area. Born and raised in Connecticut, his inherited Yankees fandom (yes, he can hear all of your grumbles) and curiosity about math and science combined to foster a fascination with how players contribute to run scoring and prevention, as did growing up reading the venerable pages of sabermetric havens such as FanGraphs, Baseball Prospectus, and Beyond the Boxscore. The accessibility of pitch-by-pitch Statcast data has allowed him to dig deeper into player and team tendencies and examine how each approaches the opposition, which he has written about at his own website, Sabermetric Musings. He hopes to use his skills and interests to contribute to the baseball discourse at large, as well as the website that played such a big part in making him the baseball observer he is today.

Vladimir Guerrero Jr. is a supremely talented hitter. In this season’s early going, he has already hit a ball 114.1 mph, swatted a home run, and has a couple of RBI to his name. Prior to his call-up in 2019, Eric Longenhagen and Kiley McDaniel rated him as the best prospect in baseball with a 70 Future Value. If you go to The Board, only five other players since 2017 have received such a grade: Wander Franco (now an 80), MacKenzie Gore, Gavin Lux, Yoán Moncada, and Shohei Ohtani. His specific combination of future tool grades, consisting of a 70 hit tool, 70 game power, and 80 raw power, is unrivaled in the dataset, a unique blend of elite bat-to-ball skills and game-changing power. At 19, he posted a 203 wRC+ in Double-A and a 175 wRC+ in Triple-A. The latter is especially impressive given that the average age of a Triple-A player is 28.

With those things in mind, you might say that what we have seen from the young phenom thus far is a bit disappointing. In 757 plate appearances through his age-21 season, Guerrero has posted a 107 wRC+. That places him 112th amongst all hitters since 2019 (for players with at least 500 plate appearances), sandwiched between the aging Robinson Canó and Omar Narváez. But I would note that context is key. Guerrero is one of only 10 players to receive 500 plate appearances through age 21. On that list, he ranks seventh in wRC+ behind Juan Soto, Fernando Tatis Jr., Cody Bellinger, Ronald Acuña Jr., and Carlos Correa. One could argue that four of those guys are on a Hall of Fame trajectory while the fifth (Correa) has been one of the top talents in the sport when he is not struggling with injury.

Guerrero is in rare company given the amount of big-league time he has logged at such a young age; that is an accomplishment in and of itself. But we are still left wanting more. How can he unlock his generational tools and become the hitter we hope he can be? I would argue the most glaring potential adjustment is to his swing plane. In 2019 and ’20, Guerrero posted groundball rates of 50.4% and 54.6%, respectively. The following represents his rolling average groundball rate in 25 groundball samples:

A whopping 68.5% of these samples yielded groundball rates above the major league average. Over the past two seasons, major league hitters have produced a .218 wOBA and .244 BABIP on groundballs compared to a .500 wOBA and .344 BABIP on batted balls in the air. Among the group of players with 500 plate appearances the past two seasons, Guerrero ranks 15th out of 226 players in the cohort. The frustrating part of this phenomenon is that he hits the ball exceptionally hard, to the point where if he put the ball in the air at closer to league average rates he would be a candidate to place amongst the league leaders in home runs and overall production.

To get a better idea of how Guerrero compares to sluggers with his prodigious power, I pulled the batted ball data from Baseball Savant (via Bill Petti’s baseballR package) for a select few right-handed hitters who posted comparable maximum exit velocities to Guerrero in ’19 and 2020. This list includes the following:

Top Right-Handed Sluggers 2019-20
Player Max EV 2019 Max EV 2020
Aaron Judge 118.1 113.1
Fernando Tatis Jr. 115.9 115.6
Gary Sánchez 119.1 117.5
Giancarlo Stanton 120.6 121.3
José Abreu 117.9 114.0
Marcell Ozuna 115.9 115.6
Mike Trout 116.6 112.9
Nelson Cruz 117.0 114.4
Pete Alonso 118.3 118.4
Ronald Acuña Jr. 115.9 114.8
SOURCE: MLB Advanced Media

Max exit velocity is our best indication of a player’s raw power. We do not have to worry about a sufficient sample of plate appearances to see how that power plays in the game; all we care about is how hard the player can put the ball in play if he makes optimal contact. You, the reader, might gripe that it is difficult to use max exit velocity to gauge a player’s power. How do we know this is truly the hardest he can hit the ball? To that I say, yes, smart reader we definitely do not know if a player’s maximum exit velocity is actually the hardest he will hit the ball. But, I will say, we can reasonably confident that we are in range fairly quickly, based on research from Alex Chamberlain.

The main comparison I am interested in is the differences in approximate attack angle between these players. The concept was outlined in great detail by Jason Ochart at Driveline in this 2018 post, but the TLDR is it is the vertical angle (which is associated with the launch angle of a batted ball) of the bat as it goes to impact the baseball. Hitters can measure it with bat sensors or by parsing video.

Unfortunately, we do not have this information for major league hitters in games because they do not walk up to the plate with sensors on their bats. Instead of throwing our collective hands up, however, we can approximate attack angle with the data we do have access to. And fortunately, that has already been done. Back in 2017, David Marshall wrote an amazing piece on the Community Research blog here at FanGraphs reverse engineering attack angle from Statcast data. He concluded his post with an elegant linear equation approximating attack angle based on the launch angle of the top 20% of a player’s hardest hit batted balls. Anthony Shattell has also posted about data of this nature in the past, and I would highly-recommend scrolling through his feed for some batted ball related visuals; he uses the top 10% of hardest hit balls for his attack angle approximations. For this analysis, I arbitrarily took the top 5%. One might quibble with such a choice, but I think it gets the same point across.

Here are the estimated attack angles for the hitters in the table above based on my filtering criteria:

Attack Angle of Vlad EV Comparables
Player Attack Angle
Pete Alonso 15.62
Aaron Judge 9.86
Giancarlo Stanton 8.74
Nelson Cruz 14.85
José Abreu 11.26
Mike Trout 16.94
Gary Sánchez 16.11
Marcell Ozuna 15.23
Ronald Acuña Jr. 17.86
Fernando Tatis Jr. 15.25
SOURCE: MLB Advanced Media

Stanton has the flattest swing in this group with an estimated attack angle of 8.74 degrees. Guerrero is even lower at 8.71 degrees. Stanton and Judge stick out in that they hit a ton of home runs but have noticeably flatter swings then the rest of the group. They make up for those flat swings by hitting the ball harder than anybody else in baseball. In the Statcast era (since 2015), Stanton has hit 28 balls over 118 mph, the most in the majors. Judge sits second with 10 (he was not a full-time regular until 2017). Third, despite his lack of experience in the big leagues, is Guerrero. If you just look at 2019 and ’20, Vlad is tied for the most with Stanton. Guerrero and his power are in rare company. What’s more, Stanton and Judge have career strikeout rates of 28.1% and 31.4%. Guerrero’s sits at just 17.0%. Even though he doesn’t have quite the same amount of juice on contact as the Yankees outfielders, he makes up for it by putting the ball in play much more often, albeit on the ground. Stanton and Judge have career groundball rates of 42.2% and 38.5%, respectively, with the former about league average and the latter about a standard deviation below it.

Guerrero is still a step behind Stanton and Judge with regards to power, so any large increase in extra base hits (where he has been slightly above league average in terms of the percentage of his total plate appearances) will have to come from either hitting the ball harder or putting more balls in the air. In my own research, I found that maximum exit velocity peaks around age 26 and average exit velocity on balls in the air peaks around 30. So maybe there is some power Guerrero can still squeeze out of his bat. Given that he is already inside the top 1% in raw power, however, I am dubious of how much room for growth there is in that department. What about swing plane? There is precedence for young hitters changing their distribution of batted balls.

More often than not, these young talented hitters saw performance boosts when putting the ball in the air more. That is not to say Guerrero will definitely see a bump in production if he focuses on hitting the ball in the air. It could mess with his swing for all I know. But I do believe that there is room for him to add some loft in his swing, even at the expense of more whiffs. His strikeout rate is close to six percentage points below the league average. There is a trade-off to be had there that can make him the fearsome hitter we all believe he can be.

Guerrero is still very young and has a lot of room to grow as a hitter. The projection systems seem to agree. The FanGraphs Depth Charts projections see him putting up a .360 wOBA in 2021, 23rd in baseball. THE BAT X, which to my knowledge most explicitly leverages existing Statcast data, is even more optimistic. It sees a .376 wOBA in Vlad’s future, placing him 11th in the league and sandwiching him in between Yordan Alvarez and Judge.

When you consider his pedigree coming into the majors, his high-end bat control (as evidenced by his strikeout rate), and his nearly unmatched power, I still think these projection systems are a little light on what to expect from Vlad Jr. going forward. His combination of skills should put him in the conversation to be among the best hitters in baseball, the type who is in the MVP conversation throughout his 20s. Let’s hope he can make the necessary adjustments and grow into that kind of player starting this season.

Carmen is a part-time contributor to FanGraphs. An engineer by education and trade, he spends too much of his free time thinking about baseball.

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3 years ago

For Guerrero, at least last year, his issue wasn’t all about his high GB%. Sure, it didn’t help him, but what really hurt him was that when he did get the ball in the air, they weren’t hit all that hard. More air balls sounds good, but weakly-hit fly balls usually don’t do much in terms of getting favorable results. PL had a good post on this in the offseason, IIRC.

Going back to his minor league numbers, Vlad had pretty high groundball rates, it’s not like that fact was hiding somewhere. It’s probably just who he is naturally as a hitter, and rather than him desperately trying to do anything he can to cut his groundball rate, the focus should maybe shift to why he wasn’t able to hit the ball as hard in the air last season. For what it’s worth, I’ll bet his GB% comes down from the 50+% we’ve seen for two seasons now, but it could still be relatively high as compared to some of the other hard-hitters around the league.

Smiling Politelymember
3 years ago

Is there a correlation between high GB% and weak FBs?

3 years ago

Certainly worthy of a look. My hunch is that the players such as Yelich are not the norm. That’s why when a player that hits the ball hard but too many on the ground such as Yelich or Yandy comes along, they become so talked about.