Did MLB supply a different ball for October?

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Rob Arthur of Baseball Prospectus has been the leader in researching the changes we’ve seen in the baseball — and the skyrocketing home run rate — over the past several years. Today he makes an observation that suggests, perhaps, things are moving back in a less-launchy direction, at least for the postseason. And it may be no accident.

With the caveat that we’re dealing with a small sample size — only 17 postseason games have been played — Arthur, using MLB’s own data, looked at how many homers one would expect to see based on exit velocity, launch angle, and the ballpark in which the ball was struck. He found that, compared to the home run rates we’ve seen all season long, there have been about 50% fewer home runs than expected. Fifty percent!

And no, those “cool October temperatures” have nothing to do with it because (a) his model controls for weather; and (b) it, actually, has been warmer in October thus far than it had been, on average, over the course of the season.

Has Major League Baseball, stung by increasing criticism over the juiced ball that has been in play over these past couple of seasons, corrected — or, perhaps, overcorrected — for it? We can’t know for sure, because no one ever talks about this stuff, but the change, which Arthur says corresponds perfectly with the start of the postseason, is most curious.