The juiced ball casts doubt on how the Yankees will perform in 2020

The two players we’re probably going to remember the most from the 2019 New York Yankees will be DJ LeMahieu and Gio Urshela. The former was a bona fide star in his first season in the Bronx, getting MVP votes and the only A+ in our own season review report cards, while Urshela was a delight in a career year of his own. We’re all expecting big things out of them in 2020.

Brett Gardner and Gleyber Torres were also pleasant surprises, in one particular area. They both hit for more power than was expected—interestingly enough, the same was true of LeMahieu and Urshela. They all made launch angle adjustments, and Torres in particular is a young star on the rise, but there was a little something going on with the baseball this year too.

Let’s drop Torres from this analysis for right now, but even with those three guys—a combined 12.1 fWAR and 75 home runs—the changes in their production can’t just be explained by swing changes:

We know that all three guys had unprecedented years in terms of power, and it’s not like it’s a Yankee Stadium effect; Gardner’s played in the Bronx his whole career and LeMahieu was coming from Coors Field of all places. So we have to explore other options.

One way to zero in on the ball’s affect on performance is looking at the difference between wOBA and xwOBA. The closer those two numbers are together, the more it reflects a “true” player’s production, or how much other variables affected performance if wOBA is higher or lower:

So LeMahieu’s actual production was a little lower than his expected. It’s pretty marginal so we can say he “earned” his wOBA, and that makes sense. He hits the ball hard and raised his launch angle this year, so even if he got a few extra feet on a couple fly balls, it seems like his performance was pretty true.

The other two players are a different story. Neither Gardner nor Urshela hit the ball as hard as LeMahieu, and that’s reflected in how much they overperformed their xwOBA. We know that Gardner in particular has been a big beneficiary of the juiced ball in the past, and it seems that was the case for both guys, on top of the analytical changes both made.

This lends to wider-than-expected error bars in projecting their performance. If the ball is any different in 2020, it becomes really hard to pin down what we can expect out of players that benefited so much from it. Unsurprisingly, Steamer is projecting a step back for all of the players in our set:

Steamer won’t actually tell us how it’s calculating the ball in its 2020 projections, but all three players are expected to have lesser seasons, and that will only be compounded if the baseball isn’t quite so rabbity. Even if you think LeMahieu’s projection is a tad conservative, it’s just harder to pin down what these guys are going to do with a different baseball.

This also highlights how important bats like Aaron Judge and Giancarlo Stanton are. Hitters like them would be 70+ grade power in any era of the game, and if there is going to be less power across baseball, it makes the real power guys more valuable.

Of course, the ball may be the same next year, and Gardner may not be a Yankee, making this concern pretty irrelevant for the team. Anyone counting these three guys filling big roles in 2020, though, has to keep an eye on the ball.