Interesting read on the baseballs being slick if you haven't seen this one yet. There is definitely something to it when all these pitchers suddenly can't throw or locate their slider as effectively. Seems like its definitely allowed some hitters to eliminate the slider and just sit fastball, which would make sense for some of the run production we've seen off top notch pitching talent. 
 
https://www.si.com/mlb/2017/10/29/world-series-baseballs-leather-justin-verlander-yu-darvish-ken-giles-kenley-jansen