Interesting piece from Verducci here on the World Series baseballs being different from regular season balls, making it hard to throw a slider well:
https://www.si.com/mlb/2017/10/29/world-series-baseballs-leather-justin-verlander-yu-darvish-ken-giles-kenley-jansen
Pitchers and coaches from both sides doing the complaining. They've even done blindfold tests in the bullpen and the players can identify the WS balls every time. Especially pitchers like Giles and Darvish, who rely on the slider as their out pitch, are being affected.
This would seem to favor guys with fastball command, especially, going forward.
https://www.si.com/mlb/2017/10/29/world-series-baseballs-leather-justin-verlander-yu-darvish-ken-giles-kenley-jansen
Pitchers and coaches from both sides doing the complaining. They've even done blindfold tests in the bullpen and the players can identify the WS balls every time. Especially pitchers like Giles and Darvish, who rely on the slider as their out pitch, are being affected.
This would seem to favor guys with fastball command, especially, going forward.