Hey, maybe you’ve heard about the juiced or “bunny” ball in the major leagues over the past few seasons. Major League Baseball and Rawlings have been playing with the seam heights and coefficient of restitution (COR - or the bounciness of the ball) of the baseball the past few years to try to “fix” the rise in offense (nevermind the argument that there isn’t anything to fix but that’s another article for another time). Listen, there are too many damn articles to link on this subject over the past few years (MLB even did a study!) so let’s just focus on 2021.
In February, MLB said they were going to “alter” the baseball in 2021, lowering the seam heights in an effort to lower COR. Also, the number of teams that will use humidors will double from five to ten (the five new humidor teams are the Houston Astros, Miami Marlins, St. Louis Cardinals, and Texas Rangers). The strange thing is MLB said nothing of trying to increase drag, which lowering the seams would do the opposite of.
In the spring, a study showed that the new balls weren’t working as intended. Then in April after a few weeks of Statcast data, that was mostly confirmed, that the ball wasn’t acting as intended - it was flying as far as ever.
But what balls have the minor leagues been using since then and how have they fared?
Triple-A has been reportedly using the new MLB baseball, but any level below that has been stuck with the old ball. But here is the catch - many minor league teams, who didn’t play a single inning in 2020 due to the COVID-19 pandemic, are working through the backlog of 2020 balls they had already purchased. They will use whatever is left of 2020 baseballs - the supposedly more juiced ball - before switching to their new 2021 stock.
So how has the run environment in Triple-A been? Well...juiced right now.
The reclassification of the teams at each level hurts a bit of continuity here, particularly since this is the only year with the new unified leagues. Using per-game stats helps here level that out though, and runs and home runs are up compared to the three-year prior average. In 2019, there was a big spike in offense, while 2021 has dropped slightly in runs, home runs, doubles, and triples, but 2019 was a tough standard to beat. Still, in Triple-A West, home runs are up 55% over the three-year average and 20% above 2019 even despite the 56% jump that year. Runs-per-game in that division are at an eye-popping 6.03 per game.
It is odd that doubles and triples are down but home runs are up. Perhaps we are seeing balls travel farther (which jives with the new baseball) and either dying at the wall or going over it. As Rob Arthur pointed out in an earlier linked piece above:
MLB said they’d be tuning down the COR by an unspecified amount, which should have cut against the change in weight. Instead, we got exactly the exit velocity increase expected from the weight cut they promised, without any tempering from a COR reduction. Instead of being deadened, the baseball is as live as ever, with higher exit velocity and a little less travel.
Triple-A teams could have exhausted the old supply quickly - if there were any balls to begin with, as some teams used these balls last summer in alternate camp. They may be seeing balls hit at the right launch angle flying over the wall, while others that would have been doubles/triples under the old ball, turn into outs.
Now for Double-A, where they are reportedly using the same ball as 2019.
Again, more explosion, with Double-A catching up to Triple-A’s 2019 boom. Home runs-per-game are up almost 40% vs the three-year average and up 41% since 2019, while overall scoring is up 11.6%.
But what could be causing this? Some teams in Double-A from 2019 are either defunct or moved to another level, but almost all remained in Double-A. Also, the number of teams haven’t changed (30 total) and besides, we used per-game to neutralize that.
The weather was actually during the cooler part of the year, as offense usually picks up starting in July as we roll into the dryer and hotter months.
Quality of competition changes? Doesn’t seem likely because it’s not as if the 2021 minor league rosters are any better than any other year or minor league pitching stinks.
Is it the baseball? I have no clue, but Double-A was supposed to be using the same ball as ever, unchanged unlike in Triple-A.
Okay, let’s ignore the year-over-year rate stuff and say it’s not comparable because sure, why not. How about the number of hitters with an OPS equal to or above .900 by year for each level amongst qualified hitters.
It’s pretty easy to interpret the graph. Before 2018, there were only a handful of hitters each year (sometimes as few as one!) who had an OPS at or equal to .900. Then 2019 came and Triple-A popped from eight batters to thirty-six. This year in Double-A, it has gone from one in 2019 to twenty-five in 2021.
I’ve always liked to use wRC+ to at least put the context of the players’ performance in the minors to some normalized scale. Obviously, you can’t only look at the stat line but wRC+ will weigh the triple-slash line appropriately while also making some league adjustments (though not park adjustments). However...maybe it needs a tweak?
It’s subtle, but the distribution has gotten a bit flatter (ie: wider ranges). The same can be said for DRC+ (which IS supposed to adjust for park factors).
Or a slightly different way to look at it (this is just wRC+):
The red highlights seep out a bit darker in the 150-169 wRC+ bin as well as the 170-189 wRC+ bin has tripled, all borrowing from the lower bins.
There is no question minor league offense has exploded, the question is why? Minor league affiliate/level adjustments? Even more productive/efficient hitters? Or could it be the ripples of physical baseball changes have continued to wreak havoc? It really is bizarre now that almost 25% (!!!) of batters in Triple-A have an OPS >= .900 now and it is worth figuring out if this is just transitory or the new normal.