Mound Visit: What would a dejuiced ball mean for hitters? ☕

The Pirates were not as reliant on home runs as other teams in 2019, but a less lively ball would still hurt their hitters.


In the last Mound Visit, we examined what a de-juiced baseball would mean for Pirates pitchers. This week, it is the hitters’ turn.

But before we revisit the idea of a less lively baseball in 2020, we have to address the Astros/Nationals World Series. 22 home runs were hit over the seven game series. Of the 26 barreled balls batters hit, 17 went for home runs (65.4%). That’s a slightly higher rate than during the regular season (59.6%), but this can mostly be attributed to small sample size. Still, the ball went from juiced to de-juiced to rejuiced in a month’s time.

What happened during those first two rounds of the playoffs? Dr. Meredith Wills is on the case again and she has a hypothesis, which she presented at the Carnegie Mellon Sports Analytics Conference on Nov. 2. While it is true fly balls had more drag earlier in the postseason, she found there were huge fluctuations in drag between games. Her conclusion: Major League Baseball used their back inventory of balls from previous seasons to try to slow down offenses. For the most part, it worked.

Assuming Wills is correct, what does that mean for the game in 2020? Does Major League Baseball want to go back to an older style of ball, or at least try to slow down the home run explosion? It seems only fair for general managers to know what equipment the league will be providing them before they assemble their teams this offseason.

But back to the original question: What would a de-juiced ball mean for the Pirates? In the last Mound Visit, I hypothesized Pirates pitchers would have allowed 40 fewer home runs last season if they used the postseason ball all season long (instead of the regular season one). For the sake of consistency, we’ll be ignoring the World Series results and use the same data pulled from the original postseason ball from the last article. What would happen if the Pirates hit that ball all year? Would they have been a better team if that was the uniform ball across the league?

The Pirates’ offense last season is hard to categorize. When the rest of the league was hitting home runs, they were hitting singles. Their 163 team home runs were the fourth fewest in baseball. They barrelled 243 balls, second worst in baseball to just the Marlins. Their 31.6 fly-ball percentage was 29th in baseball as well, with only Miami, again, being worse.

Despite that, their position players finished with a team .759 OPS, just a hair below league average. They finished 20th in runs scored (758), but they would have easily finished in the middle of the pack had Josh Bell or Starling Marte been healthy in September. The Pirates, despite being really bad at hitting home runs, held their own at the dish and were pretty close to average overall.

Obviously the juiced ball had something to do with that. Some lazy fly balls that would have been outs turned into hits and line drives found gaps instead of being hit softly to center. Again, we’re going to keep a lid on Pandora’s box and just look at how a de-juiced ball would impact their home run total, and not their BABIP.

Let’s start by looking at HR/FB%. Last season, the Pirates had a home run to fly ball percentage of 11.6%, the third worst in baseball. In the last Mound Visit, I concluded the juiced ball added 2.4 points to HR/FB rate, so with a deadened ball, it would drop to 9.2%. Here is how a 2.4-percent drop would have impacted their hitters from last year (min. 50 fly balls):

Somewhat surprisingly, the hitter who saw the biggest dip in their theoretical home run total was Adam Frazier. This is because he hit the most fly balls on the team last year. Bell is a close second, and Marte’s home run total goes from a career best 23 to his 2018 total, 20.

Going based on the HR/FB% model, Pirates pitchers would have allowed 36 fewer home runs with the postseason ball. Pirates batters would have hit 34 fewer, as well. So in the end, it is a pretty even split, though the Pirates were a hair worse-off with the livelier ball.

But HR/FB% is not a perfect tool. We should look at the quality of contact to see how many of those fly balls had a realistic chance of being a home run.

Last year, the Pirates hit 243 barrels and 229 “solid” contact balls, and these batted balls accounted for 155 of their 163 home runs. Here is how often they turned into home runs, and what those rates would have been with a de-juiced ball:

Adding in those other eight home runs the Pirates hit that did not fall under either category, that means the Pirates would have projected to hit 131 home runs in 2019. That may seem low, but that was where the bottom of the league hovered around from 2016-2018.

So if the Pirates used the 2019 postseason ball instead of the regular season one, going based on the batted ball profiles of their pitchers and hitters, they would have allowed 40 fewer home runs and hit 32 fewer. That means the ball created a gap of eight home runs in the opposition’s favor.

Eight home runs does not seem like that big of a difference, but consider this: Since 1995, teams that out-homer their opponent win roughly three-fourths of their games, according to Mike Petriello. That number has crept up a bit in recent years, too. It is safe to assume closing that gap by eight home runs would have swung two or three games in the Pirates’ favor. That is basically the same as going out and getting a middle of the rotation starter this offseason.

So the conclusion is similar as last time: The juiced ball hurt the Pirates in 2019, but they had plenty of other, more pressing problems. Those problems lead to the manager, general manager and team president getting fired, and a change in leadership could mean more than a change in equipment.

Data courtesy of FanGraphs and Baseball Savant.


Oct. 22: What would a dejuiced ball mean for pitchers?
Oct. 15: How Kuhl could break big
Oct. 10: The lesson from Cole/Glasnow
Oct. 8: Ex-Pirates of the postseason


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Leo Walter
Leo Walter

Alex, what do you think will happen when the computerized balls and strikes system is implemented ? Considering the reaction to its use in the AFL and also the analysis, hitters are going to need some help, at least for a considerable period of time. And for skeptics, it’s coming, sooner or a little later ! Just as the universal DH will be.

Long John Silver
Long John Silver

With all the problems that they still have and the fan reaction to it, I hope the computerized ball/strike never happens in my lifetime.


Interesting analysis. Unfortunately MLB would have to switch to an entirely different ball (perhaps a volleyball?) before the Pirates offense will ever be more than average at best.


Alex pointed out that they would have been average last year if not for the Marte and Bell injuries. So, we are not far off from average on offense.


Alex … A drop in HR/FB rate from 11.6% to 9.2% is indeed a 2.4 point drop as you stated. But, it should be considered a 20.68% drop when applied to the individual hitters rates.

For instance, in the table, Diaz is projected to go from a HR/FB rate of 2.6% to 0.2% (a 2.4 drop) – meaning 100% of his HRs were due to the baseball change.
If instead, you used the 20.68% rate change. It would mean his HR/FB rate of 2.6% would decrease to 2.1% – and he would still have hit his 2 HRs.


The Pirates went back to being the Pirates of 1993-2012 when they typically had two or three above average guys like Brian Giles and Aramis Ramirez playing with a bunch of marginal players like Al Martin, Kevin Young, Joe Randa, Ryan Doumit and on and on and on. As an old school guy who likes stats but finds the current analytics trend boring, I will always believe in the eyeball test.