Jr. vs. Jr.
A baseball friendship between sons.
Imagine your father being a major league superstar; a humble man that hails from the Dominican Republic and an absolute champion on the baseball field. Imagine the lights and the deafening roars of the crowd, and the glorious vivaciousness that baseball never fails to imbue in its fans; all directed towards your father while your height isn’t above four feet. The mettle of a baseball superstar, and father, that inspires you to play ball. I can only imagine these were the feelings of Vladimir Guerrero Jr. and Fernando Tatis Jr. when they were growing up.
Vladimir Guerrero Sr., also known as Vlad the Impaler, is a hall of famer with 449 HR; and Fernando Tatis Sr., although not a hall of famer, made two grand slams in a single inning against the Dodgers in 1999. Their sons had great admiration for their fathers’ baseball careers, and it makes sense why they’d want to be a stars like their fathers. They both debuted in 2019, where they both received rookie of the year awards, and two years later they were voted in as all stars for the National and American league; both are living recognition of their fathers, yet both are creating their own names for themselves to go beyond what their family ever dreamed of. But this leads to the killer question, out of the juniors which one is better?
Basic Metric Comparison
We will start off with a basic box score metric comparison with data we can find on Baseball-Reference, we will be using the years 2019 - 2021, all their completed seasons (Tatis has been sidelined for the 2022 season as of 7/18/2022).
To help interpret the tables, the counting stats like…
and
are summed across three years, while the rate statistics are averaged throughout the three years. This makes sense because you’d want a cumulative sum of counting statistics, and an average of rate metrics (because adding a rate doesn’t really make sense). If you want the average of the counting stats, then its in the row below where it says Average.
In terms of the counting statistics, it seems like Vladimir Guerrero has Fernando Tatis beat in experience in a major league setting. His G, PA, and AB are all higher than Tatis, but generally this is where Guerrero’s supremacy in counting stats end. Tatis has Guerrero beat in doubles, triples, and homeruns, some of the most important hits to measure offensive play. This is even more impressive to think about since Tatis has less overall game experience, as he was able to rake in more valuable hits despite playing for a shorter amount of time. However, it should be mentioned that both players’ total runs scored across the three seasons are roughly equal.
In the rate statistics, we see Fernando Tatis beating Vladimir Guerrero in every way: most of them are not a significant difference until we look at SLG where Tatis clearly beats Guerrero. This makes sense because we saw Tatis gaining more doubles, triples, and HR than Guerrero;, therefore leading him to a better SLG and OPS. Once again,, there is still one thing to consider: Tatis has less experience in games—this implies less data. In this case, Guerrero has a whole 253 AB more than Tatis, which is very significant when we consider how AB is used in most equations:
Something/AB
AB is always (when looking at simple metrics) for the rate statistics, meaning that a higher AB would penalize the rate stats. This means that Guerrero has a slight penalty over Tatis; realistically, if Tatis was to have the amount of AB Guerrero has, his rate statistics would regress to a smaller value. Not to say that this contingency makes Tatis’s rate metrics worse than Guerrero’s, but there isn’t such a major difference between their SLG as it may seem.
Overall, it would seem that Fernando Tatis Jr. has a minor victory over Vladimir Guerrero Jr. in terms of the simple metrics. Next we will look at the more complex metrics.
Complex Metrics Comparison
The metrics we will be using for this complex comparative test are: wOBA, Barrel %, BB%, wRC+, and WAR from 2019 - 2021. In subsequent analyses beyond this article I might add more to this list of metrics or use different metrics; I chose these simply because these are the best in objectively looking at a batter. When we compare Fernando Tatis and Vladimir Guerrero we get the following table of data:
First looking at wOBA it is clear that Tatis takes the win in this metric, not by a large margin, but still performing better than Guerrero. This means that Tatis is on base 2.5% more often than Guerrero. I should mention that these wOBA values are excellent for both batters here as wOBA interpretation is the same as on base percentage. This means that Tatis and Guerrero are on base for every at bat around 40% of the time— this is incredible! Barrel % is where we start to see big differences between Tatis and Guerrero, where Tatis has a 7% lead. According to the MLB glossary a Barrel is:
assigned to batted-ball events whose comparable hit types (in terms of exit velocity and launch angle) have led to a minimum .500 batting average and 1.500 slugging percentage since Statcast was implemented Major League wide in 2015.
This may seem non-intuitive since it is difficult to think of transforming a batted ball to batting average and slugging percentage, but if we think of it in terms of exit velocity and launch angle this is equivalent to:
an exit velocity of at least 98 mph. At that speed, balls struck with a launch angle between 26-30 degrees always garner Barreled classification. For every mph over 98, the range of launch angles expands.
A quick and dirty way to interpret if a hit is a Barrel is if the ball goes over 98 mph, because it’s most likely going to fall into the Barrel angle range anyways.
Barrel percentage (how Statcast interprets it) is the number of barrels per plate appearance, and it should be noted that Fernando Tatis Jr. was second in the league in barrel percentage in 2021, with Shohei Ohtani in first.
There’s not much difference in walk percentage (BB%) here, we see Guerrero takes this one, but at a measly 0.3%. The value of a high walk percentage is that it shows plate discipline, which is an important skill to have because you get on base.
Tatis gets a significant jump in terms of wRC+, where he gets a whopping 18 more runs than Guerrero. Weighted runs created is an incredibly important metric because runs are the main currency of the game, and to see Tatis with a significant lead shows his skill as a hitter and as a valuable player on his team.
Lastly, with the all-encompassing statistic, we somehow see Tatis with a WAR of 13. This doesn’t make sense even though the way FanGraphs cumulates the data is by summing it rather than averaging. Let us look at the WARs throughout the 3 year period:
By looking at the yearly WAR we see Fernando Tatis Jr. with a clear victory— an overwhelming victory at that! We even see that Tatis ranked within the top 5 bracket of WAR in 2020 - 2021!
Overall, we see this overwhelming victory by Tatis over Guerrero when we consider the more complex metrics; something that we weren’t really able to see when it came to looking at the standard counting metrics.
Final Thoughts
When we consider all the metrics we’ve looked at, Tatis takes this victory as being the better batter. This can be exemplified in Tatis’ WAR, where he scores a whole point above Guerrero in 2021: he’s just a great offensive player. However, it would be valuable to point out how Tatis and Guerrero changed over these three years, best shown in graphical form:
We see from the graphic that, by showing the change in wOBA and OPS over time, Guerrero Jr. actually has improved a ton since his debut in 2019 compared to Tatis Jr.. While wOBA and OPS for Tatis actually tend to hover around a certain value, Guerrero has made a drastic increase throughout his career, especially during the 2020 - 2021 season.
So even though Tatis, on average, is the better hitter according to the data, we must consider how this data changes through time because we can also see that Guerrero wasn’t underperforming during this same time period. Guerrero was improving himself year after year, eventually exceeding Tatis in wOBA and OP— arguably the two most important batting metrics in baseball.
Lastly I would like to exemplify the friendship between Tatis and Guerrero with this video.
Notes
I would’ve used the 2022 season, but Tatis has suffered a major injury and hasn’t played at all in 2022.