I don't think a change in pitcher skill level necessarily means a change in the pitcher results. The impetus of this change is the batters' new swing. Both 2016 and 2017 were extremes for Cole and likely will represent a career best and worst, but either way, his stuff did not appear to react well to a league-wide epidemic of uppercut swings. I wouldn't expect things to even out, I'd expect things to more resemble last year, and I'm not going to rely on historical trends when last year looked to be a significant offensive revolution. And Cole is not alone, sinkers are taking a beating league-wide. Like Kyle Gibson, Cole really cut down on his sinker usage at the end of last year, unlike Gibson, his results weren't very good.