10-game ban for foreign substances:
https://www.espn.com/mlb/story...d-suspended-10-games
Washington Post says:
But the notion of enhanced enforcement appears to have been some kind of deterrent. In the 12 days before June 3, Major League hitters hit .233, walked 9.1 percent of the time, struck out 24.3 percent of the time, and experienced a home run-to-fly ball ratio of 12.7 percent. In the 12 days after, those same hitters hit .246, walked 8.4 percent of the time, struck out 23.3 percent of the time, and experienced a home run-to-fly ball ratio of 14.4 percent.
The sudden increase in offensive performance is noteworthy in multiple ways. It does seem to suggest that the threat of punishment is limiting pitcher advantage over hitters — which, one could assume, meant those substances were giving pitchers that advantage in the first place.