The Dynasty Problem with High Ground Ball Rates

Matt looks at how ground ball rates can impact player performances.

For this article, we are going to do Going Deep with a dynasty twist. For those readers who are unaware, I currently do most of my work on Pitcher List with the dynasty team. Evaluating the long-term value of both major and minor league value of players is a large part of what the dynasty team does. One particularly interesting and difficult thing to do is figure out which prospects are more likely to see success in the major leagues.

Most dynasty managers know there is more to a prospect than just their surface stats. Just as with a major league player, statistics like ERA and batting average only mean so much. Jon Anderson has done some significant research into what statistics are “sticky” for minor league players. Essentially, his work looks at which statistics are truly indicative of a minor league player’s skill level and can help predict the level of success that player will see if promoted to the major leagues. Stolen bases are the most significant which makes sense. Speed does not change regardless of what level a player is at. The most used statistics for prospect evaluation is strikeout/walk rate. Plate discipline is one area analysts love to dive into and form their opinions around (see Elly De La Cruz).

One other area that has been gaining more attention recently is players’ batted ball tendencies. Launch angle is another statistic that Jon mentioned having a relatively strong correlation. What does this mean? If a player hits a lot of ground balls in the minor leagues, they are likely to continue hitting ground balls at a high rate in the major leagues. Should fantasy/dynasty managers be worried about this? Let’s dive in and see if this is something worth forming your opinions around.

How Ground Balls Play in the Major Leagues

One of the most used analytic statistics is BABIP. This is one-way fantasy baseball players are able to determine if a hitter has been lucky or unlucky. The average BABIP is considered to be .300, but there are some batters who tend to run higher BABIPs than others. BABIP can be extremely useful but varies based on factors such as a player’s speed, and most importantly, their batted ball distribution.

Nathan Dokken put out a piece on Fantrax a couple of years ago discussing how BABIP varies depending on how a ball is hit. For example, the highest BABIP comes on a line drive, and back in 2018, that number sat at .672. Fly balls were the worst with a BABIP down at .117, but ground balls were not much better with an average down at .236. Basically, put it is hard to get a hit off a ground ball.

The other and fairly obvious thing that hitting a ground ball prevents is hitting a home run. Players can have incredible raw power, but it is impossible for that power to ever translate to home runs if they continue hitting the ball into the ground. Here is a quick statistical analysis that can be done to show the difference:

We know that HR/FB% oftentimes is a good indicator of a player’s power. Players that post high HR/FB% have more raw power and are likely to hit more home runs. Let’s assume that two players are going to get 600 plate appearances in a season. Hitter A has phenomenal raw power but has a very low average launch angle. Hitter B is the opposite. His raw power is nothing to write home about, but he is able to get the ball in the air with regularity.

  • Player A: 25% FB% with a 12% HR/FB would hit 18 home runs in a season
  • Player B: 48% FB% with a 6% HR/FB would hit 17.28 home runs in a season

Despite Player B hitting home runs at half the rate per fly ball as Player A, they end up with almost the same number of home runs at the end of the season. A player’s batted ball distribution matters and can drastically change the stats they end up putting up in a season.

The Statistical Differences

Some of what has been outlined in this article is fairly obvious. I am sure you are smart enough to know that a player cannot hit a home run on a ground ball. However, how does this change overall performance? So far in 2023 (as of writing this part on June 25th) there are 36 players with 150+ plate appearances and a ground ball rate of at least 50%. Their average wRC+? 98. An average of 98 is relatively in line with the league average of 100. On the surface, it seems like these hitters are just as likely to see offensive success as other players.

However, what if you take out generational talents? While it is nice to assume that every prospect is going to turn into Ronald Acuña Jr. or Juan Soto, it is unrealistic to expect this. These players are rare talents that do not come around very often. They are outliers to the statistical norms. Soto and Acuna Jr. are the top two players with ground ball rates north of 50% in terms of wRC+. So, what if you take out the “outliers”? The average wRC+ of the remaining 36 players drops to 94. There are 13 players left with an average wRC+ over 100 and 23 with a wRC+ below the league average. If you increase the ground ball rate to 55%+, the average wRC+ drops to 86.

Emphasizing these statistical differences for 2023 is important because of the new rules. The shift ban could open up more holes along the infield and provide hitters with a better chance to find success with ground balls. However, we have already seen that average wRC+ tends to drop with high ground ball rates and this issue is not new. Looking back to 2022, there were 62 hitters with a ground ball rate north of 50%. Their average wRC+ was just 91. The 56 hitters from 2021 had an average wRC+ of 86.

Comparing this now to batters with a more level swing path, there are 69 hitters in 2023 with a line drive rate of at least 22% and a ground ball rate below 45%. The average wRC+ of those 69 hitters is 109.

Is the average wRC+ of 109 from the 69 batters statistically different from the 98 wRC+ found from the players with a ground ball rate of 50% or greater? Using the Central Limit Theorem, we can assume normality of these and complete a hypothesis test to determine if these two values are statistically different. To form a population, I pulled the wRC+ for all batters in baseball with at least 150 plate appearances. The average wRC+ was 104 with a population standard deviation of 25.3.

If you are interested in more of my math, please feel free to reach out, but a two-sample T-Test was used to complete this hypothesis test. Our null hypothesis is that the two samples are not statistically different, while the alternative is that the wRC+ of players with a smooth swing path is statistically larger than the players with high ground ball rates. The T-Value returned from the test was 3.855 while the critical value is 1.66. This allows us to reject the null hypothesis and assume with 95% confidence that players with a higher ground ball rate post a lower wRC+ on average.

Which Minor League Players Does This Impact?

Taking this article to a dynasty perspective, we can look at some top prospects who might struggle at the major league level if they don’t undergo a swing change. I want to preface this by saying not all prospects with a high ground ball rate are going to struggle in the major leagues. Jordan Walker is performing just fine this year with a 134 wRC+ despite his high ground ball rate. The whole purpose is to point out that it is more difficult for a player to have success, but not that it is impossible.

Looking at minor league hitters with 100+ at-bats, a GB%>50%, and a wRC+>100, several names stick out. The first and most obvious is Jackson Holliday. So far, Holliday has a ground ball rate of 50.3%. After his torrid start, Holliday is batting just .229/.386/.314 with one home run since May 24th. This is not to say Holliday is not a top-of-the-line prospect (he still ranks inside my Top-10). I just am a little bit more hesitant to crown him the next generational talent in baseball until he proves he can hit the ball in the air with more consistency.

Other names on the list that stick out are Nelson Rada (LAA), Justin Crawford (PHI), Adael Amador (COL), Brooks Lee (MIN), and Brady House (WAS). The most severe case of the names just listed is Crawford. He currently is running a ground ball rate of 69.3% with a .425 BABIP. Speed will help Crawford’s BABIP, but that level of performance is unsustainable with a ground ball rate that high. He is going to need to undergo a swing change if he ever wants to reach his ceiling.

Looking for a couple of underrated prospects that might not garner as much attention, but already have super smooth swing paths? Here are three that you should be paying more attention to:

How To Use This Information

Running a few numbers and deciding that a player is more likely to see success if they hit fewer ground balls should not completely alter your opinion of a player who hits a lot of ground balls. Imagine being out on Soto because he hits the ball into the ground. Always bet on talent first and foremost. A player with raw talent is far more valuable than a below-average player with a smooth swing path.

This study is meant to help create caution flags during prospect evaluation. If a player is posting incredible minor league statistics, take a look at their batted ball distribution. There is a possibility this player is just having some fortunate luck early on but is going to experience struggles as he progresses through the minor leagues.

Most importantly, look for adjustments and development. One of my favorite examples this year of a player making a deliberate change in their batted ball distribution is Jordan Lawlar. In 2022, Lawlar had tons of success at Low-A and High-A despite ground ball rates near 50%. Still, he made an adjustment this season and is now only hitting ground balls about 37% of the time. Now, he is on pace for 23 home runs while batting .330/.390/.580 since May 23rd (his early season struggles were a result of a .203 BABIP).

Players are constantly working to adjust and improve. Look for this when evaluating prospects. If you like what a prospect is doing one season with a high ground ball rate, look for them to make the adjustment to hit more balls in the air the following year. There are always going to be cases of rare talents that find success with low launch angles, but it is important to remember that this is not the norm. If you are deciding between two similar prospects, I recommend going with the one that has a smoother swing path and is more likely to find success at the major league level.

Graphic adopted by Aaron Polcare (@bearydoesgfx on Twitter)

One response to “The Dynasty Problem with High Ground Ball Rates”

  1. Jay Jones says:

    This is extremely useful thank you

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